fixing debian bug #708635 (skip quilt directory)

It's MANIFEST.SKIP.PL being too smart. The attached patch should help:

When applying patches with quilt(1), a directory called '.pc'
will contain the original state for unapplying. If a quilt
patch happens to modify a file ending for instance in '.xs',
MANIFEST.SKIP will have a useless (and in certain cases harmful)
entry for a corresponding .c file under the .pc/ directory.

Skip all files that match m#^\.pc/#.
* MSWin32: detect gcc also if specified with full path
  This is fixing https://rt.cpan.org/Ticket/Display.html?id=74036
* more places with /^gcc/
* PNG: use pkg-config for --cflags and --libs

  If pkg-config is not available, then fallback to the old hardcoded
  values. (This does not change anything for the last fallback of
  using the bundled libpng)
* Tk::MakeDepend: parse gcc's inc search list

  gcc may have more built-in search paths for includes than
  /usr/include, e.g. in multiarch environments (Debian/sid). Also,
  /usr/include may be invalid for custom gcc installs (may happen for
  example on Windows systems)

  This fixes https://rt.cpan.org/Ticket/Display.html?id=85407 and
  http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=708624
* build instructions for ActivePerl + gcc
* inc'd VERSION to 804.030_502
* updated Changes for Tk-804.030_502