Wrap fnmatch().

A POSIX function.  Third parameter is a string describing portable
flags.  Check source to see what they are.
Wrap wordexp().  This returns a table of results.
Bug fix---don't allow command expansion.
Make fsys.gexpand(), a generator of filenames.

Typical usage:

	for file in fsys.gexpand("~/source/boston/src/[a-c]*.c") do
		print(file)
	end