* Update docgen to generate manpages for Heretic/Hexen.

Heretic:
 * Frequency shifted sounds.
 * Check all command line parameters
 * Check for endianness assumptions
 * Savegame code to write structures predictably and endianness-correct
 * Remove NeXT and WATCOMC defines
 * Structure packing macros for structures read from disk
 * Merge r_draw.c to common version and delete duplicate
 * v1.2 emulation (if possible)
 * Screensaver mode

Hexen:
 * CD-ROM music playback
 * Frequency shifted sounds.
 * Check for endianness assumptions - mostly done now
 * Savegame code to write structures predictably and endianness-correct
 * Remove NeXT and WATCOMC defines
 * Structure packing macros for structures read from disk
 * Merge r_draw.c to common version and delete duplicate
 * v1.0 emulation (if possible/necessary)
 * Screensaver mode