code: Remove deprecated calls to alloca().

The alloca() function is deprecated and, according to the man, sometime buggy
for some platform. The calls are replaced by Z_Malloc() / Z_Free() pairs.

Chocolate DOOM did the same.
code: Change code version to match doom1.wad file version.

The doom1.wad file is released in version 109, the code shall match this
version to start demo after the introduction screen. Thus version is changed
from 110 to 109.

FIXME: Set the version by parameter at runtime? i.e:

       ./doom --version 109
Merge branch 'master' of github.com:bmarcot/DOOM