As was discussed at the summit, we'd like to get rid of global language
callbacks so that we can
safely inline from different source languages.
AFAICS, this can be archived by using the space occupied by the
lang_flags to store a language
tag in each tree node.
I.e., while the frontend does processes the source, we use the language
hook from that frontend,
but once everything is converted to GIMPLE, each tree node is tagged
with the source language,
and language hooks are looked up using this language hook in the tree
node that defines the context
for which langiage-specific information is needed.
This assumes that after conversion to GIMPLE, we don't need any more
lang_flags. Is that true?
