version 0.99 pre2: pause options, gameplay fixes/features

version 0.99 pre2: pause options, gameplay fixes/features

# when enemy changed into a pickup, movement is set to vslow
* instead of turning into a pickup, enemies explode and a pickup
   appears at the right side of the screen (moves left slowly)
# bullets do damage again (screenflash made damage become 0)
+ when destroyed by bullets, the armor bar will show 0HP left
* all enemy bullets do the same damage in all levels
* you now appear at (*32*,30) because enemies can come from left
* improved bullet handling (faster, smaller, etc.)
+ multiples are animated like real Nemesis (pulsating)
# fixed a bug that didn't select multiples when you were moving
# enemy collision screwed up invert and some other weird stuff
+ in pause screen change contrast with up/down and B/W mode with F1
+ lasers can have different durations (beams last longer)
* some sign-flag checkings replaced by carry-flag (thus reducing size)
# slow enemies (including pickups) didn't always appear (just 25-50%)
+ enemies can fire different kinds of bullets: aiming, double, triple
* maximum number of bullets increased (48 for enemies, 128 for you)