Lazy-evaluating list of files, based on globs or regexes
Description
A FileList is a lazy-evaluated list of files. When given a list of
glob patterns for possible files to be included in the file list,
instead of searching the file structures to find the files, a FileList
holds the pattern for latter use.
This allows you to define a FileList to match any number of files, but
only search out the actual files when then FileList itself is actually
used. The key is that the first time an element of the FileList/Array
is requested, the pending patterns are resolved into a real list of
file names.
