Better tests for Intl specs.

[keithamus]

Following on from #371 (and #358), the Intl specs could do with improving.

The following needs to be added to get an idea of levels of support from browsers/engines:

Intl Object

• [ ] Add full set of tests for Intl.Collator object (mimicking test262 test suite)
• [ ] Add full set of tests for Intl.NumberFormat object (mimicking test262 test suite)
• [ ] Add full set of tests for Intl.DateTimeFormat object (mimicking test262 test suite)

Date Object

• [ ] Add full set of tests for Date#toLocaleString() (mimicking test262 test suite)
• [ ] Add full set of tests for Date#toLocaleDateString() (mimicking test262 test suite)
• [ ] Add full set of tests for Date#toLocaleTimeString() (mimicking test262 test suite)

Number Object

• [ ] Add full set of tests for Number#toLocaleString() (there is no test262 suite for this - see tc39/test262#195. Maybe we should PR a set before porting them to compat-table?)

String Object

• [ ] Add full set of tests for String#localeCompare() (mimicking test262 test suite)

Array Object

• [ ] Add full set of tests for Array#toLocaleString() (mimicking test262 test suite)

Object Object

• [ ] Add full set of tests for Object#toLocaleString() (mimicking test262 test suite)