Remove `git_time_monotonic`

`git_time_monotonic` was added so that non-native bindings like rugged
could get high-resolution timing for benchmarking.  However, this is
outside the scope of libgit2 *and* rugged decided not to use this
function in the first place.

Google suggests that absolutely _nobody_ is using this function and we
don't want to be in the benchmarking business.  Remove the function.

include/git2/sys/time.h

-/*
- * Copyright (C) the libgit2 contributors. All rights reserved.
- *
- * This file is part of libgit2, distributed under the GNU GPL v2 with
- * a Linking Exception. For full terms see the included COPYING file.
- */
-#ifndef INCLUDE_git_time_h__
-#define INCLUDE_git_time_h__
-
-#include "git2/common.h"
-
-GIT_BEGIN_DECL
-
-/**
- * Return a monotonic time value, useful for measuring running time
- * and setting up timeouts.
- *
- * The returned value is an arbitrary point in time -- it can only be
- * used when comparing it to another `git_time_monotonic` call.
- *
- * The time is returned in seconds, with a decimal fraction that differs
- * on accuracy based on the underlying system, but should be least
- * accurate to Nanoseconds.
- *
- * This function cannot fail.
- */
-GIT_EXTERN(double) git_time_monotonic(void);
-
-GIT_END_DECL
-#endif
-

src/util.c

@@ -864,11 +864,6 @@ int git__utf8_iterate(const uint8_t *str, int str_len, int32_t *dst)
 	return length;
 }
 
-double git_time_monotonic(void)
-{
-	return git__timer();
-}
-
 size_t git__utf8_valid_buf_length(const uint8_t *str, size_t str_len)
 {
 	size_t offset = 0;