configure: Always use old_CFLAGS and old_LIBS

The variables used for storing CFLAGS and LIBS before temporarily
modifying them was consistent when it comes to the name, but not
when it comes to the case.

Make sure names are completely consistent.

configure.ac

@@ -321,7 +321,7 @@ if test "x$lv_cv_pthread_sigmask_works" != xyes; then
   AC_DEFINE([FUNC_PTHREAD_SIGMASK_BROKEN], [1],
     [Define to 1 if pthread_sigmask is not a real function])
 fi
-LIBS=$old_libs
+LIBS=$old_LIBS
 
 dnl Availability of various common headers (non-fatal if missing).
 AC_CHECK_HEADERS([pwd.h regex.h sys/un.h \
@@ -1198,15 +1198,15 @@ AC_SUBST([LIBXML_CFLAGS])
 AC_SUBST([LIBXML_LIBS])
 
 dnl xmlURI structure has query_raw?
-old_cflags="$CFLAGS"
-old_libs="$LIBS"
+old_CFLAGS="$CFLAGS"
+old_LIBS="$LIBS"
 CFLAGS="$CFLAGS $LIBXML_CFLAGS"
 LIBS="$LIBS $LIBXML_LIBS"
 AC_CHECK_MEMBER([struct _xmlURI.query_raw],
 		[AC_DEFINE([HAVE_XMLURI_QUERY_RAW], [], [Have query_raw field in libxml2 xmlURI structure])],,
 		[#include <libxml/uri.h>])
-CFLAGS="$old_cflags"
-LIBS="$old_libs"
+CFLAGS="$old_CFLAGS"
+LIBS="$old_LIBS"
 
 dnl GnuTLS library
 AC_ARG_WITH([gnutls],
@@ -1222,8 +1222,8 @@ if test "x$with_gnutls" != "xno"; then
     GNUTLS_LIBS="-L$with_gnutls/lib"
   fi
   fail=0
-  old_cflags="$CFLAGS"
-  old_libs="$LIBS"
+  old_CFLAGS="$CFLAGS"
+  old_LIBS="$LIBS"
   CFLAGS="$CFLAGS $GNUTLS_CFLAGS"
   LIBS="$LIBS $GNUTLS_LIBS"
 
@@ -1289,8 +1289,8 @@ if test "x$with_gnutls" != "xno"; then
     with_gnutls=yes
   fi
 
-  CFLAGS="$old_cflags"
-  LIBS="$old_libs"
+  CFLAGS="$old_CFLAGS"
+  LIBS="$old_LIBS"
 fi
 
 if test "x$with_gnutls" = "xyes" ; then
@@ -1431,8 +1431,8 @@ if test "$with_selinux" != "yes" ; then
         AC_MSG_ERROR([You must install the libselinux development package and enable SELinux with the --with-selinux=yes in order to compile libvirt --with-secdriver-selinux=yes])
   fi
 elif test "$with_secdriver_selinux" != "no"; then
-  old_cflags="$CFLAGS"
-  old_libs="$LIBS"
+  old_CFLAGS="$CFLAGS"
+  old_LIBS="$LIBS"
   CFLAGS="$CFLAGS $SELINUX_CFLAGS"
   LIBS="$CFLAGS $SELINUX_LIBS"
 
@@ -1440,8 +1440,8 @@ elif test "$with_secdriver_selinux" != "no"; then
   AC_CHECK_FUNC([selinux_virtual_domain_context_path], [], [fail=1])
   AC_CHECK_FUNC([selinux_virtual_image_context_path], [], [fail=1])
   AC_CHECK_FUNCS([selinux_lxc_contexts_path])
-  CFLAGS="$old_cflags"
-  LIBS="$old_libs"
+  CFLAGS="$old_CFLAGS"
+  LIBS="$old_LIBS"
 
   if test "$fail" = "1" ; then
     if test "$with_secdriver_selinux" = "check" ; then