some uses of SLRE need to be made case-insensitive

[bruceravel]

Alas, I don't understand how to make SLRE's (?i) thing work. In the "strings" branch I am working on lowercasing things before doing matching.

An example is in XDI_validate_item when checking a extension item against the versioning string. It should be OK to have an extension item called foo.x and an extra_version string which includes Foo/7.95.