AIX: Test the -qlonglong option before use.

xlc provides "long long" unconditionally at C99-compatible language
levels, and this option provokes a warning.  The warning interferes with
"configure" tests that fail in response to any warning.  Notably, before
commit 85a2a8903f7e9151793308d0638621003aded5ae, it interfered with the
test for -qnoansialias.  Back-patch to 9.0 (all supported versions).

configure

@@ -4877,6 +4877,41 @@ if test x"$pgac_cv_prog_cc_cflags__qnoansialias" = x"yes"; then
   CFLAGS="$CFLAGS -qnoansialias"
 fi
 
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $CC supports -qlonglong" >&5
+$as_echo_n "checking whether $CC supports -qlonglong... " >&6; }
+if ${pgac_cv_prog_cc_cflags__qlonglong+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  pgac_save_CFLAGS=$CFLAGS
+CFLAGS="$pgac_save_CFLAGS -qlonglong"
+ac_save_c_werror_flag=$ac_c_werror_flag
+ac_c_werror_flag=yes
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  pgac_cv_prog_cc_cflags__qlonglong=yes
+else
+  pgac_cv_prog_cc_cflags__qlonglong=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+ac_c_werror_flag=$ac_save_c_werror_flag
+CFLAGS="$pgac_save_CFLAGS"
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_prog_cc_cflags__qlonglong" >&5
+$as_echo "$pgac_cv_prog_cc_cflags__qlonglong" >&6; }
+if test x"$pgac_cv_prog_cc_cflags__qlonglong" = x"yes"; then
+  CFLAGS="$CFLAGS -qlonglong"
+fi
+
 elif test "$PORTNAME" = "hpux"; then
   # On some versions of HP-UX, libm functions do not set errno by default.
   # Fix that by using +Olibmerrno if the compiler recognizes it.

configure.in

@@ -461,6 +461,7 @@ elif test "$ICC" = yes; then
 elif test "$PORTNAME" = "aix"; then
   # AIX's xlc has to have strict aliasing turned off too
   PGAC_PROG_CC_CFLAGS_OPT([-qnoansialias])
+  PGAC_PROG_CC_CFLAGS_OPT([-qlonglong])
 elif test "$PORTNAME" = "hpux"; then
   # On some versions of HP-UX, libm functions do not set errno by default.
   # Fix that by using +Olibmerrno if the compiler recognizes it.

src/template/aix

@@ -7,7 +7,7 @@ if test "$GCC" != yes ; then
       CFLAGS="-O -qmaxmem=16384 -qsrcmsg"
       ;;
     *)
-      CFLAGS="-O2 -qmaxmem=16384 -qsrcmsg -qlonglong"
+      CFLAGS="-O2 -qmaxmem=16384 -qsrcmsg"
       ;;
   esac
 fi