pgsql: Remove some configure header-file checks that we weren't really

Remove some configure header-file checks that we weren't really using.

We had some AC_CHECK_HEADER tests that were really wastes of cycles,
because the code proceeded to #include those headers unconditionally
anyway, in all or a large majority of cases. The lack of complaints
shows that those headers are available on every platform of interest,
so we might as well let configure run a bit faster by not probing
those headers at all.

I suspect that some of the tests I left alone are equally useless, but
since all the existing #includes of the remaining headers are properly
guarded, I didn't touch them.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/2bd7f85796ec373ecae61dd480437b3e668ec883

Modified Files
--------------
config/ac_func_accept_argtypes.m4 | 9 +--------
config/c-library.m4 | 10 +++++-----
configure | 38 +++++---------------------------------
configure.in | 8 +-------
src/backend/libpq/ifaddr.c | 2 --
src/bin/psql/command.c | 2 --
src/include/libpq/libpq-be.h | 2 --
src/include/pg_config.h.in | 15 ---------------
src/include/pg_config.h.win32 | 12 ------------
9 files changed, 12 insertions(+), 86 deletions(-)