This is a follow-up on the QUIC MUX renaming process. Now most of "qmux"
generic usages as been replaced in favor of "qcm" naming. The next part
of the renaming is to replace "qstrm" naming with "qmux" for stuffs
related to the new QMux protocol specifically.
This is first applied on filenames. As with the previous renaming,
Makefile and include statements are updated as well to prevent
compilation issues.