Import precedences are assigned in post-order over the import tree, so
sibling imports are distinct and every unit sits above its own
imports; apply-imports searches only the current template's
stylesheet's own import subtree per 5.6, reverting to the built-in
rule when that unit imports nothing; an included stylesheet's
declarations join the including unit at its precedence while its
imports join the import list; and include/import hrefs resolve against
the including stylesheet's URI. Included documents' roots stay
retained until their declarations are parsed (tree parents are weak,
so the in-scope xmlns chain could vanish mid-compile). Xalan baseline
159 -> 144 (reluri 11 -> 3, impincl 9 -> 2).
Mihaela Mihaljevic
ef4e7afa7a