The 11/13 branches and master use 2 different file version macros. 11/13
uses ASTERISK_FILE_VERSION but master uses ASTERISK_REGISTER_FILE. This
means a new file added to 11/13 can't just be cherry-picked to master
because the macro has to be changed.
To make cherry-picking possible, ASTERISK_REGISTER_FILE was added
to asterisk.h as a simple alias for ASTERISK_FILE_VERSION(__FILE__, NULL)
The "$Revision$" tag doesn't do anything since Asterisk moved to git so
just passing NULL as the verison works fine. asterisk.h was also
annotated to deprecate ASTERISK_FILE_VERSION and suggest using
ASTERISK_REGISTER_FILE for all new files.