This migrates all remaining uses of cImport (and addTranslateC for good
measure) to using translate-c for C translation, ensuring that we are
ready for when cImport is removed from the language, and also that all
sources of C translation are using the same snapshot of the external
package (when can then be updated when we need to fix something).
A couple of notes:
* A few options have been added to support the new translations, namely
the ability to link libraries (passed through to linkLibrary on the
Translator side) and whether or not to initialize default values
(looks like cImport did this without a way to control it, but
translate-c does not do it by default).
* Using the new library linking option actually simplifies the process
of translating a number of the C packages as we have been shipping the
necessary headers for these packages already with the applicable
libraries. For some of the more complex translation processes though,
we still include the appropriate directories directly.
There are scenarios where this configuration looks bad. This commit
introduces some heuristics to prevent it. Here are the heuristics:
* Extension is always enabled on alt screen.
* Extension is disabled if a row contains any default bg color. The
thinking is that in this scenario, using the default bg color looks
just fine.
* Extension is disabled if a row is marked as a prompt (using semantic
prompt sequences). The thinking here is that prompts often contain
perfect fit glyphs such as Powerline glyphs and those look bad when
extended.
This introduces some CPU cost to the extension feature but it should be
minimal and respects dirty tracking. This is unfortunate but the feature
makes many terminal scenarios look much better and the performance cost
is minimal so I believe it is worth it.
Further heuristics are likely warranted but this should be a good
starting set.
