Commit af07095 extends ‘search-path-specification’ with a ‘file-type’ field, which can be 'regular.
Then, commit 7b21fe5 adds a ‘file-pattern’ field, to look for files matching a pattern recursively. Lastly, commit 2a8d440 uses these features for libxml2 and $XML_CATALOG_FILES. Comments welcome! Ludo’.
