configure: Use AC_USE_SYSTEM_EXTENSIONS to set GNU_SOURCE & other defines
Ensures reallocarray is visible in system headers if available. (See libxext#4 (closed).)
Signed-off-by: Alan Coopersmith alan.coopersmith@oracle.com
Ensures reallocarray is visible in system headers if available. (See libxext#4 (closed).)
Signed-off-by: Alan Coopersmith alan.coopersmith@oracle.com