A utility to run an arbitrary program on each of the LLVM source files.

This is like llvmgrep but instead of running grep, it runs the command
given by the first argument. For example, to find the top ten files with
the most lines in llvm, you could:

utils/llvmdo wc -l | sort -nb | tail

Or, to find any source files with the wrong permissions, you could:

utils/llvmdo ls -l | grep -v rw-r--r--

Hopefully, you get the idea.

llvm-svn: 15246