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/libstrongswan/plugins/openssl/Makefile.am

@@ -1,7 +1,9 @@
+AM_CPPFLAGS = \
+	-I$(top_srcdir)/src/libstrongswan \
+	-DFIPS_MODE=${fips_mode}
 
-INCLUDES = -I$(top_srcdir)/src/libstrongswan
-
-AM_CFLAGS = -rdynamic -DFIPS_MODE=${fips_mode}
+AM_CFLAGS = \
+	-rdynamic
 
 if MONOLITHIC
 noinst_LTLIBRARIES = libstrongswan-openssl.la
@@ -31,4 +33,3 @@ libstrongswan_openssl_la_SOURCES = \
 
 libstrongswan_openssl_la_LDFLAGS = -module -avoid-version
 libstrongswan_openssl_la_LIBADD  = -lcrypto
-