gprof redux

[dank@kegel.com]

See http://www.kegel.com/gprof.html for what I know
about glibc support for gprof.  There are two problems:
multithreaded support (for which there's a workaround that works
on uniprocessors, at least), and support for more than 64K symbols
(no workaround yet).
Ullrich Drepper is highly pessimistic that any improvements
can or should be done here, but I think that it might be
possible to craft a patch that even he would approve of.

I'm going to stare at the code for a bit and see what's up
with that 64K symbol limit.  The gprof file format is
flexible enough that it could be extended to handle this
case without changing the format used for < 64K symbols,
I think.
- Dan