Announcing coan 4.2

Coan now factors active #define and #undef directives into the evaluation of subsequent #if-conditions in the same source file. These directives are added to the commandline --define and --undef options for the duration of the source file where they appear. This eliminates one of the last remaining blindspots in Coan's simulation of the C preprocessor and paves the way to remove the others.

Simplification of #if-conditions now preserves parentheses for readability where the meaning would otherwise depend on operator precedence.

All open bugs on v4.1 are fixed.

A lot of effort has gone into simplifying tortuous code (though it is still abundant).

A complete listing of the changes can be found in the Changelog at http://coan2.sourceforge.net/