#82 Syntax highlighting for macros

[Victor Lyuboslavsky]

Currently all of the following get the same syntax highlight color (Keyword color):

• SystemVerilog keywords
• macros, like `uvm_info
• compiler directives, like `include
• system functions, like $display

Macros should get a different highlight color. (It is ok if macros and compiler directives share a color.)

As a bonus, it would also be nice for system functions to get their own color as well.