Add abillity to add custom crypto files.

Change-Id: I6c5b1cdb0a90f7604bdde088332c171332b43dcc
Reviewed-on: https://code.wireshark.org/review/3945
Reviewed-by: Anders Broman <a.broman58@gmail.com>

epan/CMakeLists.txt

@@ -52,6 +52,7 @@ set(CRYPT_FILES
 	crypt/airpdcap_debug.c
 	crypt/airpdcap_rijndael.c
 	crypt/airpdcap_tkip.c
+	${CUSTOM_CRYPT_SRC}
 )
 source_group(crypt FILES ${CRYPT_FILES})
 

epan/CMakeListsCustom.txt

@@ -26,4 +26,8 @@ set(CUSTOM_DISSECTOR_SRC
 
 set(CUSTOM_DIRTY_ASN1_DISSECTOR_SRC
 #	dissectors/packet-foo.c
+)
+
+set(CUSTOM_CRYPT_SRC
+#	crypt/foo.c
 )