Integrate pg_bsd_indent into our build/test infrastructure.

Integrate pg_bsd_indent into our build/test infrastructure.

Update the Makefile and build directions for in-tree build,
and add Meson build infrastructure.  Also convert the ad-hoc
test target into a TAP test.

Currently, the Make build system will not build pg_bsd_indent
by default, while the Meson system will.  Both will test it
during "make check-world" or "ninja test".  Neither will install
it automatically.  (We might change some of these decisions later.)

Also fix a few portability nits noted during early testing.

Also, exclude pg_bsd_indent from pgindent's purview; at least for
now, we'll leave it formatted similarly to the FreeBSD original.

Tom Lane and Andres Freund

Discussion: https://postgr.es/m/3935719.1675967430@sss.pgh.pa.us
Discussion: https://postgr.es/m/20200812223409.6di3y2qsnvynao7a@alap3.anarazel.de