automake: replace INCLUDES by AM_CPPFLAGS

INCLUDES are now deprecated and throw warnings when using automake 1.13.
We now also differentiate AM_CPPFLAGS and AM_CFLAGS, where includes and
defines are passed to AM_CPPFLAGS only.

src/libtls/Makefile.am

@@ -1,5 +1,5 @@
-
-INCLUDES = -I$(top_srcdir)/src/libstrongswan
+AM_CPPFLAGS = \
+	-I$(top_srcdir)/src/libstrongswan
 
 ipseclib_LTLIBRARIES = libtls.la
 libtls_la_SOURCES = \