pgsql: More minor cosmetic improvements: - remove another senseless

Log Message:
-----------
More minor cosmetic improvements:

- remove another senseless "extern" keyword that was applied to a
function definition
- change a foo more function signatures from "some_type foo()" to
"some_type foo(void)"
- rewrite another K&R style function definition
- make the type of the "action" function pointer in the KeyWord struct
in src/backend/utils/adt/formatting.c more precise

Modified Files:
--------------
    pgsql/src/backend/executor:
        spi.c (r1.130 -> r1.131)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/spi.c.diff?r1=1.130&r2=1.131)
    pgsql/src/backend/port:
        sysv_shmem.c (r1.38 -> r1.39)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/port/sysv_shmem.c.diff?r1=1.38&r2=1.39)
    pgsql/src/backend/utils/adt:
        formatting.c (r1.78 -> r1.79)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/formatting.c.diff?r1=1.78&r2=1.79)
    pgsql/src/backend/utils/mb:
        mbutils.c (r1.47 -> r1.48)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/mb/mbutils.c.diff?r1=1.47&r2=1.48)
        wstrcmp.c (r1.6 -> r1.7)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/mb/wstrcmp.c.diff?r1=1.6&r2=1.7)
    pgsql/src/interfaces/ecpg/preproc:
        output.c (r1.11 -> r1.12)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/preproc/output.c.diff?r1=1.11&r2=1.12)