optimize generated vertex programs a bit

optimize generated vertex programs a bit

Use new internal state to avoid per-vertex normalization of static spot
direction vector. Use internal state for simpler per-vertex fog computations
(MAD instead of SUB/MUL for linear fog, EX2 instead of POW for EXP/EXP2 fog).
Simplify point size calc (2 MADs instead of MOV, MUL, MUL, DP3), and while
there fix it up (RSQ instead of RCP). All untested...