This commit provides a minimal refactoring of the include hierarchy to allow eliminating the LIBSRTP_INTERNAL_BUILD hack added a couple of days ago.  This was tested with gcc, g++, and clang.  Also did a sanity build of the doubango and asterisk downstream projects.
diff --git a/Makefile.in b/Makefile.in
index 9374ab7..5a7fc21 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -42,7 +42,7 @@
 
 CC	= @CC@
 INCDIR	= -Icrypto/include -I$(srcdir)/include -I$(srcdir)/crypto/include
-DEFS	= @DEFS@ -DLIBSRTP_INTERNAL_BUILD
+DEFS	= @DEFS@
 CPPFLAGS= @CPPFLAGS@
 CFLAGS	= @CFLAGS@
 LIBS	= @LIBS@