Mainly tested on:
  Box
    - Pentium 166MHz PC.
  OS
    - Linux 2.0.35 i586
  Make
    - GNU Make 3.76.1
  C compiler
    - gcc 2.7.2.3
  Ruby
    - ruby 1.4.3 (1999-12-08) [i586-linux]
  Gtk+
    - Gtk+-1.2.6
  Imlib
    - 1.9.4
  BGM ;-)
    - `Neo Generation' (by Sakura Tange)


Result of `time make' (CFLAGS='-pipe -O2 -g -Wall')
on the above environment:
    user   367.300 sec
    system  26.450 sec
    total  393.750 sec


Other environments on which tested:

Pentium 200 MMX
Linux 2.2.13
GNU Make 3.76.1
GCC 2.95.2
Ruby 1.4.3
Gtk+ 1.2.6
Imlib 1.9.4 
CFLAGS='-O6'
BGM none (^^;
