Scans the web application's subdirectory identified by rootPath,
along with its subdirectories, for TLDs.

Initially, rootPath equals /WEB-INF. The /WEB-INF/classes and
/WEB-INF/lib subdirectories are excluded from the search, as per the
JSP 2.0 spec.

@param resources The web application's resources
@param rootPath The path whose subdirectories are to be searched for
TLDs
@param tldPaths The set of TLD resource paths to add to