Add the missing file for the previous commit

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@1500 65c4cc65-6c06-0410-ace0-fbb531ad65f3

include/asterisk/causes.h

+#define AST_CAUSE_NOTDEFINED	0
+#define AST_CAUSE_NORMAL	1
+#define AST_CAUSE_BUSY		2
+#define AST_CAUSE_FAILURE	3
+
+/* Translate the pri's cause number to asterisk's */
+int hangup_pri2cause(int cause);
+
+