Patch to avoid gprof profiling overwrites

It's difficult to profile a backend server process (using gprof)
because each process overwrites any earlier profile as it exits.

It is especially tricky to nab a useful profile if you happen to have
autovacuum enabled.

This patch reduces the problem by forcing the backend to 'cd' to a new
directory ($PGDATA/gprof/pid) just before calling exit(), but only if
the backend was compiled with -DLINUX_PROFILE.

I've tested this with Linux, but not with other host architectures.

-- Korry

--
Korry Douglas korryd(at)enterprisedb(dot)com
EnterpriseDB http://www.enterprisedb.com