Sharewarendectomy

Consensus that the "shareware" target was no longer necessary was
reached long ago[1]. It just needs to actually get done. Thus:

Makefile:
- remove shareware targets

buildcfg.txt, textures/combined.txt:
- remove #ifdef/#ifndef SHAREWARE sections (almost entirely #ifndef)

graphics/help2.gif:
- remove symlink, help2 screen was shareware-only

gitignore:
- remove shareware files no longer built

textures/shareware:
- remove directory

--
[1] http://www.doomworld.com/vb/freedoom/52758-removing-shareware/ .

In particular, Jon wrote:
>The original purpose of the shareware IWAD was to have a smaller set of
>resources to target 100% completion of. That was probably met a long
>time ago.

More recently chungy wrote in <http://www.doomworld.com/vb/post/957707>
>Removing the "demo"/"shareware" version of Freedoom has been discussed
>but it's never been done. Actually it's a bit easier to just leave it
>in than to remove it. (It'd be pretty easy to get rid of it anyway, but
>nothing is really gained from it)

Signed-off-by: RjY <rjy@users.sourceforge.net>

graphics/help2.gif

@@ -1 +0,0 @@
-doomttl.gif