Revert to autoconf 2.69 for tests

Author: natefoo

configure.ac

@@ -1,5 +1,5 @@
 AC_INIT([DRMAA for Slurm],[m4_esyscmd_s(./m4/ac_version.sh)],[nate@bx.psu.edu],[slurm-drmaa])
-AC_PREREQ([2.72])
+AC_PREREQ([2.69])
 AC_REVISION([m4_esyscmd_s([git rev-parse HEAD])])
 AC_COPYRIGHT([
 DRMAA for Slurm
@@ -43,13 +43,17 @@ AC_ARG_ENABLE(development, AS_HELP_STRING([--enable-development],[enable develop
 
 # programs:
 AC_PROG_CC
+AC_PROG_CC_C99
 AC_PROG_CPP
 AC_PROG_INSTALL
 LT_INIT
 AC_PROG_MAKE_SET
 AC_PROG_LN_S
 
 # check compiler / set basic flags:
+if test x$ac_cv_prog_cc_c99 = xno; then
+	AC_MSG_ERROR([C99 compiler is required])
+fi
 
 if test x$GCC = xyes; then
 	CFLAGS="-pedantic -std=c99 ${CFLAGS}"