I just recently set up my Vim environment from Textmate, after becoming addicted to its modal input.
However, syntax highlighting seems to be not so beautiful in Vim
To match C functions definitions only, this works for me:
syn match cCustomFuncDef display /\(\w\+\(\s\|*\)\+\)\@<=\w\+\s*(\@=/ hi def cCustomFuncDef ctermfg=lightblue