.gcov fontification in compile.el

[Dan Nicolaescu]

In emacs-22 compile.el is used to fontify .gcov files. It does not
seem terribly useful (as all the the original file contents are in the
.gcov file anyway), but it might be better than what emacs-21.4 does:
just use fundamental-mode.

There are a few issues with that, all the lines in the qcov use the
`underline' face. This is kind of distracting and it does not help in
any way. 

The fontification of lines that use the full length of the counter
field is incorrect. 
Example:

116305350: 1328:  for (i = 0; i < nodes; i++) {

   (gcov-called-line
     "^ +[-0-9]+: +\\([1-9]\\|[0-9]\\{2,\\}\\):.*$" nil 1 nil 0)
       ^^^^
       Shouldn't ? be used instead of + here?