include default completion matcher if CASE_SENSITIVE

Without this, completion behavior is odd. e.g., given the four files: `fooA.ext, fooA.ext2, fooB.ext, fooB.ext2`, typing `f<tab>` results in `f.ext<cursor>` making completion to either `fooA.ext` or `fooB.ext` difficult.

(This occurs often in python source trees with `prefix*.py{,c}` files)

This change makes the behavior identical to the case-insensitive completion with the exception, of course, of case sensitivity.