Improve cmake compatibility in cc_fix_config
Improve cmake compatibility in cc_fix_config

When cmake == True:

- handles ${KEY} and @KEY@ forms
- handle #cmakedefine regardless of text after identifier
- produce comments when removing defines
- use \b to avoid errors when one key a prefix of another

This is closer to the behaviour as documented here:
https://cmake.org/cmake/help/v3.2/command/configure_file.html

And can now handle pcl_config.h.in:
https://github.com/PointCloudLibrary/pcl/blob/405d2bbb99ed5a78dc11c07a08bea9ad19f7cb6a/pcl_config.h.in
producing output similar to this:
http://docs.pointclouds.org/trunk/pcl__config_8h_source.html

antonovvk/bazel_rules