form became unnecessary with the bsd.prog.mk,v 1.69 change.
- Eliminated duplicate y.tab.h in SRCS.
Reviewed by: bde
- Complementary to the said bsd.prog.mk change, use the fact
that inner .for loops are not real loops but a tricky form
of a local macro for the outer loop's variable, and switch
to using faster variable modifiers to replace extensions.