Allow syntax coloring for operators and delimiters

[hjxkyw]

I use these commands at the end of my c and c++ syntax files, for coloring delimiters and operators, and it works fine.
In cmake syntax file these commands don't work.

syn match cntrl "[&{}()+:;,.*=<>!%@[]\-]"
hi cntrl guifg=red

I think that even it worked only for "(" and ")" it would besomething good.

[pboettch]

I see your point, please provide a PR if possible. This feature should be optional.