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@enterprisedb.com   EnterpriseDB      http://www.enterprisedb.com