c5fa470 made the extension check discard directories, but
only in the new code that currently only is used on Windows.
Let's add an equivalent check in the old code so that the
behavior is consistent across platforms.
- FileSearch is now just one function, and it converts the original glob
into a regex on all platforms rather than relying on native Windows
pattern matching on there and a complete hack elsewhere. It now
supports recursion out of the box rather than manually expanding
into a full list of directories in multiple call sites.
- This adds a GCC >= 4.9 dependency due to older versions having
outright broken <regex>. MSVC is fine with it.
- ScanDirectoryTree returns the parent entry rather than filling parts
of it in via reference. The count is now stored in the entry like it
was for subdirectories.
- .glsl file search is now done with DoFileSearch.
- IOCTLV_READ_DIR now uses ScanDirectoryTree directly and sorts the
results after replacements for better determinism.
