There's a lot of work like this to do, but not enough time in the day to reach it all.

* Replace islamicc with islamic-umalqura

Per discussion in #743, it's implementation-dependent how ismalicc is
canonicalized. However, 'islamic-umalqura' should be treated the same
way by all implementations.

* Remove ar-ma-u-ca-islamic-umalqura per discussion

This reverts commit da4f4385.

Moves ismalicc test out of main.js and creates a new
test, preferred-subtag.js (per RFC 5646 section 4.5 and
http://www.unicode.org/repos/cldr/tags/latest/common/bcp47/calendar.xml
)

Fix #743

Will fix #745

Besides, add additional checks to make sure that getCanonicalLocales()
returns an array.

This harness function is not necessary in the majority of cases in which
it is used. Remove its usage to simplify tests and decrease the amount
of domain-specific knowledge necessary to contribute to the test suite.

Persist the harness function itself for use by future tests for ES2015
modules (such a helper is necessary for tests that are interpreted as
module code).