sh(1): Improve documentation of shell patterns:

sh(1): Improve documentation of shell patterns:

* Shell patterns are also for ${var#pat} and the like.
* An '!' by itself will not trigger pathname generation so do not call it a
  meta-character, even though it has a special meaning directly after an
  '['.
* Character ranges are locale-dependent.
* A '^' will complement a character class like '!' but is non-standard.

MFC after:	1 week