Fix -m handling of recursive includes
Don't add Extern block if there are no PROCs at all
Fix token positioning bug in #include merging
Fix merging of nested #includes

#include directives from new tokens added from merged includes were
parsed by the secondary ppDirectives1() call but not expanded because
the step that looked for #includes and expands them wasn't repeated.

Parsing the PP directives and expanding #includes is now done in a loop
until everything is worked off.
Fix merging of recursive #includes

The new loop from the previous commit would run into an infinite loop.
Now in case of two #includes, #including each-other, one is merged into
the other which will end up #including itself.
Don't emit callconv with ASTATTRIB_HIDECALLCONV

For translations where AST merging is done, the merging code handles the
callconvs and ASTATTRIB_HIDECALLCONV to improve the merging.


But for translations where no AST merging is done, the emitter should
handle it itself.
Allow #includes to be merged again when parsing different version