fixed stack smashing due to wrong size of struct stat on the stack

on 32-bit systems with 64-bit file descriptor offsets enabled
(added -D_FILE_OFFSET_BITS=64 when compiling the test suite)

tests/CMakeLists.txt

@@ -9,6 +9,7 @@ SET(CLAR_FIXTURES "${CMAKE_CURRENT_SOURCE_DIR}/resources/")
 SET(CLAR_PATH "${CMAKE_CURRENT_SOURCE_DIR}")
 ADD_DEFINITIONS(-DCLAR_FIXTURE_PATH=\"${CLAR_FIXTURES}\")
 ADD_DEFINITIONS(-DCLAR_TMPDIR=\"libgit2_tests\")
+ADD_DEFINITIONS(-D_FILE_OFFSET_BITS=64)
 
 INCLUDE_DIRECTORIES(${CLAR_PATH} ${libgit2_BINARY_DIR}/src)
 FILE(GLOB_RECURSE SRC_TEST ${CLAR_PATH}/*/*.c ${CLAR_PATH}/*/*.h)