games/gzdoom: create port

GZDoom is a GL-enhanced fork of ZDoom, a source port of ID Software's DOOM
engine. It is based on the source code of id Software's DOOM. GZDoom boasts
enhanced modding support, as well as support for the following games:

• Ultimate Doom
• Doom II
• Final Doom
• Heretic
• Hexen
• Strife
• Chex Quest (1 & 3)
• Action Doom II
• Harmony v1.1
• Hacx
• The Adventures of Square

WWW: http://gzdoom.drdteam.org/

PR: 213907
Submitted by: kevans