First implementation of a new exclude facility.
To exclude a plugin from being run on a line of code, simply add a C++ comment containing the string "krazy:exclude=<plugin_name>".

Specifically, for this plugin use "krazy:exclude=doublequote_chars".
For example:
  lenstr = "0" + lenstr;
becomes
  lenstr = "0" + lenstr; // krazy:exclude=doublequote_chars

note that C style comments like the following will not work:
  lenstr = "0" + lenstr; /* krazy:exclude=doublequote_chars */

TODO: make all the plugins support this new facility
TODO: support comma-separated lists of plugins
  krazy:exclude=<plugin1>[,<plugin2>,...,<pluginN>]