Merge branch 'rh/autoconf-rhel3'

Build update for older RHEL.

* rh/autoconf-rhel3:
  configure.ac: check for HMAC_CTX_cleanup
  configure.ac: check for clock_gettime and CLOCK_MONOTONIC
  configure.ac: check 'tv_nsec' field in 'struct stat'

diff --cc git-compat-util.h
index dcecd857f159357ff7d79cde218895f43795d944,09ccebbd4958a18918d29170c9b86c91ed61cfc7..eb9b0ff32829ef62bf2d1af432742841b9720906
--- 1/git-compat-util.h
--- 2/git-compat-util.h
+++ b/git-compat-util.h
@@@ -212,12 -212,11 +212,15 @@@ extern char *gitbasename(char *)
  #endif
  
  #ifndef NO_OPENSSL
 +#define __AVAILABILITY_MACROS_USES_AVAILABILITY 0
 +#define MAC_OS_X_VERSION_MIN_REQUIRED MAC_OS_X_VERSION_10_6
  #include <openssl/ssl.h>
  #include <openssl/err.h>
 +#undef MAC_OS_X_VERSION_MIN_REQUIRED
 +#undef __AVAILABILITY_MACROS_USES_AVAILABILITY
+ #ifdef NO_HMAC_CTX_CLEANUP
+ #define HMAC_CTX_cleanup HMAC_cleanup
+ #endif
  #endif
  
  /* On most systems <netdb.h> would have given us this, but