Publish GCC 'specs' customization HOWTO.

Publish GCC 'specs' customization HOWTO.

* gccspecs.html: New file; adapted from original Drupal content, and
in particular, on user comments relating to that content, this offers
advice on customizing GCC's default behaviour, especially insofar as
it affects include file and library search paths, and the option to
deploy non-free Microsoft C runtime libraries, as alternatives to
pseudo-free MSVCRT.DLL.