[PATCH 0 of 4] win32text 'exact' encoding and deterministic filter ordering

[Mark Hammond]

This set of patches implements an 'exact' encoder for the win32text extension
and arranges for the longer filter patterns to be applied before shorter 
ones.  This allows the win32text extension to explicitly prevent some 
patterns from being filtered while still allowing use of '**' for a default
fallback.

The patch includes tests and documentation, including docs for the '!'
behaviour which was adapted from Mad's earlier doc patch.

This is my first patch for hg; please let me know if I've screwed anything
up procedurally (or obviously if I've screwed anything technically either :)

Cheers,

Mark