Doc: using the variable chooser

Move the description from the docs for external tools
to those for build settings, because the latter topic
describes variables.

Change-Id: I9586e38484b391752ca4c3f1ed14dba286890f45
Reviewed-by: hjk <hjk121@nokiamail.com>
C++: Include class name for inline functions in functionAt

The code that constructed the fully qualified name used
enclosingNamespace() which skips classes.

Use LookupContext::fullyQualifiedName() instead.

Change-Id: Ic03a91c0fe120c52dc69f3e78e82a574458d8314
Reviewed-by: hjk <hjk121@nokiamail.com>