Improvements to current identifier highlight

Hi
Current identifier highlight is a very useful feature, but there is couple issues that makes it uncomfortable in some conditions.
For me there is two major issues with current implementation:
- Visible painting lag when typing inside identifier (this is more noticeable when editing large files). There reason for this is because while line is repainted to display changed text - current identifier tokens are not refreshed and old token text is painted over modified text. This is removed by preventing painting of current identifier highlight on pressing keyboard key and restoring it after some delay (added option to select delay in configuration dialog).
- Second issue is with actually parsing current identifier. It was implemented in very CPU expensive way - so moving cursor with arrows can easily hit 100% CPU usage and noticeable delay in cursor movement (big source files). I used different way for parsing, and CPU usage drop to almost nothing - this greatly improved responsiveness of navigation with keyboard arrows .