cmake: remove CheckPrototypeDefinition module

In the past, we've imported the CheckPrototypeDefinition into our own
module directory as it wasn't yet available in all supported CMake
versions. Now that we require at least CMake v3.5, we don't need to
bundle it anymore as it's included with the distribution already.

Let's drop the included modules and always use upstream's version.

cmake/CheckPrototypeDefinition.c.in

-@CHECK_PROTOTYPE_DEFINITION_HEADER@
-
-static void cmakeRequireSymbol(int dummy, ...) {
-  (void) dummy;
-}
-
-static void checkSymbol(void) {
-#ifndef @CHECK_PROTOTYPE_DEFINITION_SYMBOL@
-  cmakeRequireSymbol(0, &@CHECK_PROTOTYPE_DEFINITION_SYMBOL@);
-#endif
-}
-
-@CHECK_PROTOTYPE_DEFINITION_PROTO@ {
-  return @CHECK_PROTOTYPE_DEFINITION_RETURN@;
-}
-
-#ifdef __CLASSIC_C__
-int main() {
-  int ac;
-  char*av[];
-#else
-int main(int ac, char *av[]) {
-#endif
-  checkSymbol();
-  if (ac > 1000) {
-    return *av[0];
-  }
-  return 0;
-}

cmake/CheckPrototypeDefinition.cmake

-# - Check if the protoype we expect is correct.
-# check_prototype_definition(FUNCTION PROTOTYPE RETURN HEADER VARIABLE)
-#  FUNCTION - The name of the function (used to check if prototype exists)
-#  PROTOTYPE- The prototype to check.
-#  RETURN - The return value of the function.
-#  HEADER - The header files required.
-#  VARIABLE - The variable to store the result.
-# Example:
-#  check_prototype_definition(getpwent_r
-#   "struct passwd *getpwent_r(struct passwd *src, char *buf, int buflen)"
-#   "NULL"
-#   "unistd.h;pwd.h"
-#   SOLARIS_GETPWENT_R)
-# The following variables may be set before calling this macro to
-# modify the way the check is run:
-#
-#  CMAKE_REQUIRED_FLAGS = string of compile command line flags
-#  CMAKE_REQUIRED_DEFINITIONS = list of macros to define (-DFOO=bar)
-#  CMAKE_REQUIRED_INCLUDES = list of include directories
-#  CMAKE_REQUIRED_LIBRARIES = list of libraries to link
-
-#=============================================================================
-# Copyright 2005-2009 Kitware, Inc.
-# Copyright 2010-2011 Andreas Schneider <asn@cryptomilk.org>
-#
-# Distributed under the OSI-approved BSD License (the "License");
-# see accompanying file Copyright.txt for details.
-#
-# This software is distributed WITHOUT ANY WARRANTY; without even the
-# implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
-# See the License for more information.
-#=============================================================================
-# (To distribute this file outside of CMake, substitute the full
-#  License text for the above reference.)
-#
-
-get_filename_component(__check_proto_def_dir "${CMAKE_CURRENT_LIST_FILE}" PATH)
-
-function(CHECK_PROTOTYPE_DEFINITION _FUNCTION _PROTOTYPE _RETURN _HEADER _VARIABLE)
-
-  if ("${_VARIABLE}" MATCHES "^${_VARIABLE}$")
-    set(CHECK_PROTOTYPE_DEFINITION_CONTENT "/* */\n")
-
-    set(CHECK_PROTOTYPE_DEFINITION_FLAGS ${CMAKE_REQUIRED_FLAGS})
-    if (CMAKE_REQUIRED_LIBRARIES)
-      set(CHECK_PROTOTYPE_DEFINITION_LIBS
-        "-DLINK_LIBRARIES:STRING=${CMAKE_REQUIRED_LIBRARIES}")
-    else(CMAKE_REQUIRED_LIBRARIES)
-      set(CHECK_PROTOTYPE_DEFINITION_LIBS)
-    endif(CMAKE_REQUIRED_LIBRARIES)
-    if (CMAKE_REQUIRED_INCLUDES)
-      set(CMAKE_SYMBOL_EXISTS_INCLUDES
-        "-DINCLUDE_DIRECTORIES:STRING=${CMAKE_REQUIRED_INCLUDES}")
-    else(CMAKE_REQUIRED_INCLUDES)
-      set(CMAKE_SYMBOL_EXISTS_INCLUDES)
-    endif(CMAKE_REQUIRED_INCLUDES)
-
-    foreach(_FILE ${_HEADER})
-      set(CHECK_PROTOTYPE_DEFINITION_HEADER
-        "${CHECK_PROTOTYPE_DEFINITION_HEADER}#include <${_FILE}>\n")
-    endforeach(_FILE)
-
-    set(CHECK_PROTOTYPE_DEFINITION_SYMBOL ${_FUNCTION})
-    set(CHECK_PROTOTYPE_DEFINITION_PROTO ${_PROTOTYPE})
-    set(CHECK_PROTOTYPE_DEFINITION_RETURN ${_RETURN})
-
-    configure_file("${__check_proto_def_dir}/CheckPrototypeDefinition.c.in"
-      "${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp/CheckPrototypeDefinition.c" @ONLY)
-
-    file(READ ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp/CheckPrototypeDefinition.c _SOURCE)
-
-    try_compile(${_VARIABLE}
-      ${CMAKE_BINARY_DIR}
-      ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp/CheckPrototypeDefinition.c
-      COMPILE_DEFINITIONS ${CMAKE_REQUIRED_DEFINITIONS}
-      CMAKE_FLAGS -DCOMPILE_DEFINITIONS:STRING=${CHECK_PROTOTYPE_DEFINITION_FLAGS}
-      "${CHECK_PROTOTYPE_DEFINITION_LIBS}"
-      "${CMAKE_SYMBOL_EXISTS_INCLUDES}"
-      OUTPUT_VARIABLE OUTPUT)
-
-    if (${_VARIABLE})
-      set(${_VARIABLE} 1 CACHE INTERNAL "Have correct prototype for ${_FUNCTION}")
-      message(STATUS "Checking prototype ${_FUNCTION} for ${_VARIABLE} - True")
-      file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeOutput.log
-        "Determining if the prototype ${_FUNCTION} exists for ${_VARIABLE} passed with the following output:\n"
-        "${OUTPUT}\n\n")
-    else (${_VARIABLE})
-      message(STATUS "Checking prototype ${_FUNCTION} for ${_VARIABLE} - False")
-      set(${_VARIABLE} 0 CACHE INTERNAL "Have correct prototype for ${_FUNCTION}")
-      file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log
-        "Determining if the prototype ${_FUNCTION} exists for ${_VARIABLE} failed with the following output:\n"
-        "${OUTPUT}\n\n${_SOURCE}\n\n")
-    endif (${_VARIABLE})
-  endif("${_VARIABLE}" MATCHES "^${_VARIABLE}$")
-
-endfunction(CHECK_PROTOTYPE_DEFINITION)