Replace deprecated g_basename with g_path_get_basename.
get rid of PL_na
Define PERL_NO_GET_CONTEXT in all perl source files

This removes the calls to Perl_get_context() that get automatically
added to XS code for ancient source code compatibility reasons.

The result is about a ~60K size reduction in the binary (based on
comparing two 64-bit stripped irssi binaries compiled
--with-perl-staticlib).
cleanup char* casts and replace one useless SvPV with SvPV_nolen
Add some missing casts to silence compiler warnings
Remove unused variables to silence compiler warnings
Add missing include

Silences:
  listen.c:320:3: warning: implicit declaration of function ‘ascii_strup’ [-Wimplicit-function-declaration]
Merge pull request #63 from dgl/cleanups

Clean-up some compiler warnings
Merge pull request #60 from dgl/perl-no-get-context

Define PERL_NO_GET_CONTEXT in all perl source files
Merge pull request #59 from ailin-nemui/perl-pl-na

get rid of PL_na
Merge pull request #44 from dajohi/g_basename

Replace deprecated g_basename with g_path_get_basename.
Initial implementation of 256 colour support for Irssi

This patch implements some 256 colour support for Irssi up from the
previous 16 colours. Initial parsing of the %x/%X format codes is
implemented and the parser accounts in advances the char* for
that.

The colour attributes are widened from 4 to 8 bit. The colour protocol
is changed to a new format. Some pointers to remaining work are
written in the comment in textbuffer.h.

Note that Irssi already does support requesting 256 colours from the
terminal in the original source code, so this part did not have to be
touched.
Finish 256 colour support for Irssi

256 colour patch is cleaned up and the remaining cases are made work,
this includes especially Theme support, which was not implemented
before. Changes not related to colours were reverted again, making a
review of the two patches against master easier to follow.

As a byproduct of the Hex-colour code parser, the 24bit colours are
also implemented. Actually using them in the terminal is guarded by a
compile time switch (as well as a run time switch), as it breaks the
existing colour protocol and requires additional storage.

To make a seamless usage, down-conversion is provided for 8 and 16
colours.

Diverging from Tom's approach, the colour protocol is reverted back to
the original one. Unfortunately, the changes required in the Theme
engine will break the API.

For more details, please refer to the patch documentation at either
http://irssi-docs.wikispaces.com/Notes-256-Colour or
https://github.com/shabble/irssi-docs/wiki/Notes-256-Colour