pxz: does not build with clang

Use llvm or gcc, as pxz uses openmp.

Closes #20209.
RethinkDB: add launchd plist

Closes #20186.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
abcm2ps: fix path in test
abcMIDI 2013-05-10
ghi 0.9.0.20130504

Closes #20211.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
alac: style nit
aplus: style nit
autoenv: style nits
basex: install metafiles in prefix
botan: simplify

* don't need to_s on ENV.compiler
* soname inreplace no longer needed
chcase: style nits
superenv: find Homebrew's gcc-4.2

If we're using a homebrewed gcc-4.2, xcrun may fail to find it (or,
worse, find superenv's shim instead). Explicitly add it to the PATH and
search all path elements for the requested tool.

Also make sure to specify 'gcc-4.2' as the compiler name, not plain
'gcc'. That can resolve to llvm-gcc and to gcc-4.0 on various Xcodes.
fftw: add test
libzdb: use recommended deps
PostgresqlDependency: use canonical name for default formula
Requirement: fix typo