pgsql: Add configure --enable-profiling to enable GCC profiling.

Log Message:
-----------
Add configure --enable-profiling to enable GCC profiling.  Patches from
Korry Douglas and Nikhil S

Modified Files:
--------------
    pgsql:
        configure (r1.534 -> r1.535)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/configure.diff?r1=1.534&r2=1.535)
        configure.in (r1.501 -> r1.502)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/configure.in.diff?r1=1.501&r2=1.502)
    pgsql/doc/src/sgml:
        installation.sgml (r1.284 -> r1.285)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/installation.sgml.diff?r1=1.284&r2=1.285)
    pgsql/src/backend/storage/ipc:
        ipc.c (r1.95 -> r1.96)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/ipc/ipc.c.diff?r1=1.95&r2=1.96)
    pgsql/src/include:
        pg_config.h.in (r1.111 -> r1.112)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/pg_config.h.in.diff?r1=1.111&r2=1.112)