sizebitvec of tsearch2, as well as identical code in several other
contrib modules.  This provided about a 20X speedup in building a
large tsearch2 index ... didn't try to measure its effects for other
operations.  Thanks to Stephan Vollmer for providing a test case.

more tests than strictly necessary, but did not feel like tracing call
paths in detail ...

of self-defined macros, add limit of Array  to gist__int_ops. BTW, intarray now
doesn't support NULLs in arrays.

getting rid of numerous ad-hoc versions that have popped up in various
places.  Shortens code and avoids conflict with Windows min() and max()
macros.