fix autoconf/automake warnings
diff --git a/Makefile.am b/Makefile.am
index f322d2c..534c86e 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1,7 +1,7 @@
AUTOMAKE_OPTIONS = foreign dist-bzip2 1.6
ACLOCAL_AMFLAGS = -I m4
-INCLUDES = $(all_includes) -I$(top_srcdir)/include
+AM_CPPFLAGS = $(all_includes) -I$(top_srcdir)/include
SUBDIRS = src include
pkgconfigdir = $(libdir)/pkgconfig
diff --git a/configure.ac b/configure.ac
index 6fc752a..ce5140a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -21,7 +21,7 @@
saved_CFLAGS="$CFLAGS"
CFLAGS="$CFLAGS -fvisibility=hidden "
AC_MSG_CHECKING([if ${CC} supports -fvisibility=hidden])
-AC_COMPILE_IFELSE([char foo;],
+AC_COMPILE_IFELSE([AC_LANG_SOURCE([char foo;])],
[ AC_MSG_RESULT([yes])
SYMBOL_VISIBILITY="-fvisibility=hidden"],
AC_MSG_RESULT([no]))
diff --git a/src/Makefile.am b/src/Makefile.am
index d4e105e..1bbcfc5 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -3,7 +3,7 @@
# documentation before making any modification
LIBVERSION=0:0:0
-INCLUDES = $(all_includes) -I$(top_srcdir)/include/asn1c
+AM_CPPFLAGS = $(all_includes) -I$(top_srcdir)/include/asn1c
AM_CFLAGS = -fPIC -Wall $(LIBOSMOCORE_CFLAGS)
lib_LTLIBRARIES = libasn1c.la