ast: Remove unused astBuildVAR() (since f9e5dfc0)
ast: Let astNewVAR() automatically derive the dtype for PROCs and LABELs

This cleans up the inconsistent dtypes on expressions taking the address
of labels.
ast: Fix some astNewVAR() calls with weird dtypes
Allow # in WINPUT( bytes, #filenum )

- Until now WINPUT() was declared as a normal function, and the normal
  function call parser doesn't allow #'s
- Now, WINPUT is a quirk keyword and WINPUT() is handled by the same
  quirk parser that handles INPUT(), and allows the #
- Since the old WINPUT() was marked FB_RTL_OPT_NOQB, the new WINPUT
  quirk keyword is now also KWD_OPTION_NO_QB
  (i.e. it still becomes __WINPUT in -lang qb)