installer: don't try and unlink nil tabfile.

Closes #23472.
libmemcached: fix "tr1/cintypes" error on 10.9.

Closes #22259.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>
ace: improve and cleanup 10.9 fix.
global: further limit tap formula regex.
formula_installer: further fix tab file handling.

Closes #23477.
mongodb: 2.4.7 (stable) and 2.5.3 (devel)

Closes #23427.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>
mongodb: remove outdated bottles.
Improve Xcode and CLT installation instructions.
mongodb: use 2.5.3 by default on Mavericks.