Possible addition to the c.vim and perl.vim syntax files

[Mark Manning]

I saw in the c.vim that there was an error statement for octal numbers.  
There isn't one for hex numbers so I made one really quickly.  If you 
want, just put it into the c.vim file.  :-)

The test:
syn region    cHexError    start="0x\x*[g-zG-Z]" end="\W"

The highlight command:

   hi link   cHexError   cError

Of course, this needs to be approved by Bram first though.  :-)

Mark