Remove "Generating" output from catalog scripts

Reduce chattiness of genbki.pl and Gen_fmgrtab.pl.

Improve consistency of comments in system catalog headers.

Make reformat_dat_file.pl preserve all blank lines.

Fix pgxs.mk to not try to build generated headers in external builds.

Fix partial-build problems introduced by having more generated headers.

Further cleanup of client dependencies on src/include/catalog headers.

Reduce worst-case shell command line length during "make install".

Merge catalog/pg_foo_fn.h headers back into pg_foo.h headers.

Switch client-side code to include catalog/pg_foo_d.h not pg_foo.h.