tas_cjmp no longer needs +jump

Before this commit, +jump command must be active in order for tas_cjmp to work.
It was largely a design decision.  We now decided that tas_cjmp should work in
a simlar way as tas_dtap does, namely tas_dtap does not depend on any
clientside command to function properly.
Decrement tas_cjmp even if !(pmove->oldbuttons & IN_JUMP)

This conforms to the way tas_dtap functions.
Don't recompute physics after running jumpbug code
genscript: handle waterjump correctly (hopefully)