Option spell checking: Penalize delimiter flags if input has no argument

If the user passes a flag like `-version` to a program, it's more likely
they mean `--version` than `-version:`, since there's no parameter
passed. Hence, give delimited arguments a penalty of 1 if the user input
doesn't contain the delimiter or no data after it.

The motivation is that with this, lld-link can suggest "--version"
instead of "-version:" for "-version" and "-nodefaultlib" instead of
"-nodefaultlib:" for "-nodefaultlibs".

Differential Revision: https://reviews.llvm.org/D61382

llvm-svn: 359701