export: Rename some variables to reflect content type.

This method is used with a list of languages.
cmTarget: INTERFACE_LIBRARY is always EXCLUDE_FROM_ALL.
cmTarget: Remove some of the INTERFACE_LIBRARY whitelisted properties.

There is no need to allow EXCLUDE_* properties, because an
INTERFACE_LIBRARY has no direct build output.

IMPORTED_LINK_INTERFACE_LANGUAGES are relevant only to static
libraries.

VERSION is relevant only to the filename of direct build outputs,
which INTERFACE_LIBRARY does not have.
Merge topic 'minor-cleanups' into next

8980964 cmTarget: Remove some of the INTERFACE_LIBRARY whitelisted properties.
55793bc cmTarget: INTERFACE_LIBRARY is always EXCLUDE_FROM_ALL.
4100a6e export: Rename some variables to reflect content type.