Now that filtered and unfiltered output can be treated identically, we
can unify the printf family of functions. This is done under the name
"gdb_printf". Most of this patch was written by script.
The "catch fork" code is reasonably self-contained, and so this patch
moves it out of breakpoint.c (the second largest source file in gdb)
and into a new file, break-catch-fork.c.
