[sc-dev] [commit] Add 'Extensions' directories to compiler path

[Rohan Drape <rd@xxxxxxxxxxxxxxxx>]

This commit:

1) Adds platform specific directories to the compiler search path.  It
   is not an error if a directory does not exist.  The directories are:

   OSX :: "/Library/Application Support/SuperCollider/Extensions" and
   "~/Library/Application Support/SuperCollider/Extensions"

   Linux :: "/usr/local/share/SuperCollider/Extensions" and
   "~/share/SuperCollider/Extensions".

2) Makes the compiler skip directories that case insensitively match
  "help" and "test".  This allows extension directories to include
  ordinary SuperCollider files (.sc files), to be used for test and
  help purposes, without requiring the user to specifically exclude or
  include particular files or directories.

Regards,
Rohan