perl: More bugfixes, correct PKG_LICENSE

So, while testing the imported oldpackages/perl-* packages, I ran into some bugs. Some old, some new.

A quick summary:
- Use "signed char" instead of "char" for signed bytes on arm/armeb
  char may be unsigned on some ARM CPUs
- Properly override CCFLAGS and header paths for modules
  Previously, modules used host-perl flags and headers
- Filter -g3 compiler flag
  Currently breaks compilation. It will turn into -g
- Strip the "encoding" pragma from perl modules
  Got deprecated in 5.18, makes HTML::Parser/HTML::Entities work
- Add overloading.pm to perlbase-essential.
  Needed by perl-dbi

I also did some cleanups, updated perl's license(it's actually GPLv1+ instead of GPLv1) and bumped
PKG_RELEASE.

This update is required for all perl-* packages. They will compile without this, but produce
garbage, non-functional binaries.
It also makes perl run on arm/armeb properly(as far as I have tested). It runs without this, but has some
serious bugs.

Tested on mipsel, arm, x86 and x86_64.