It's a bit of a pitfall with user C modules that including them in the
build does not automatically enable them. This commit changes the docs and
examples for user C modules to encourage writers of user C modules to
enable them unconditionally. This makes things simpler and covers most use
cases.
See discussion in issue #6960, and also #7086.
Signed-off-by: Damien George <damien@micropython.org>
Add working example code to provide a starting point for users with files
that they can just copy, and include the modules in the coverage test to
verify the complete user C module build functionality. The cexample module
uses the code originally found in cmodules.rst, which has been updated to
reflect this and partially rewritten with more complete information.