Fixed bug that escaped previous commit
Portability issues for Stopwatch class
Rewrote Parser::docForSwitches
Undefine "emit" if it is defined.

Use of C preprocessor symbols by non-Sawyer packages without
clearly defining a namespace prefix for the symbols is strongly
discouraged! There's no way for Sawyer to avoid using variables
that conflict with preprocessor symbols if Sawyer doesn't even
know what patterns should be avoided for its own C++ symbol names.