build: move basic preprocessor flags to regular_CPPFLAGS

This is where they belong, after all.

References: http://bugzilla.netfilter.org/show_bug.cgi?id=713
Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
diff --git a/configure.ac b/configure.ac
index 27cca9f..77502fb 100644
--- a/configure.ac
+++ b/configure.ac
@@ -41,7 +41,7 @@
 	AS_HELP_STRING([--disable-largefile], [Do not build largefile support]),
 	[enable_largefile="$enableval"],
 	[enable_largefile="yes";
-	largefile_cflags='-D_LARGEFILE_SOURCE=1 -D_LARGE_FILES -D_FILE_OFFSET_BITS=64'])
+	largefile_cppflags='-D_LARGEFILE_SOURCE=1 -D_LARGE_FILES -D_FILE_OFFSET_BITS=64'])
 AC_ARG_ENABLE([devel],
 	AS_HELP_STRING([--enable-devel],
 	[Install Xtables development headers]),
@@ -83,10 +83,10 @@
 	[nfnetlink=1], [nfnetlink=0])
 AM_CONDITIONAL([HAVE_LIBNFNETLINK], [test "$nfnetlink" = 1])
 
-regular_CFLAGS="${largefile_cflags} \
-	-D_REENTRANT -Wall -Waggregate-return -Wmissing-declarations \
+regular_CFLAGS="-Wall -Waggregate-return -Wmissing-declarations \
 	-Wmissing-prototypes -Wredundant-decls -Wshadow -Wstrict-prototypes \
-	-Winline -pipe \
+	-Winline -pipe";
+regular_CPPFLAGS="${largefile_cppflags} -D_REENTRANT \
 	-DXTABLES_LIBDIR=\\\"\${xtlibdir}\\\" -DXTABLES_INTERNAL";
 kinclude_CFLAGS="";
 if [[ -n "$kbuilddir" ]]; then
@@ -98,6 +98,7 @@
 pkgdatadir='${datadir}/xtables';
 
 AC_SUBST([regular_CFLAGS])
+AC_SUBST([regular_CPPFLAGS])
 AC_SUBST([kinclude_CFLAGS])
 AC_SUBST([kbuilddir])
 AC_SUBST([ksourcedir])