Many changes suggested by Chris. It's okay, I'll recover from the emotional
damage...maybe someday. :-)

Collapse ParseCStringVector into ParseStringVector.  Comment it.
Make it take a const input.
Use std::string::npos instead of -1 (what a mouthful!)
Make ParseEnvironmentOptions take const inputs.
Check its args at the very beginning.
Strdup all the contents of newArgv and free them all at the end.

include/Support/CommandLine.h:
Constify progName and envVar arguments to ParseEnvironmentOptions().

llvm-svn: 7905