Support timestamp begins and ends for getTransitions()

Summary: `DateTimeZone::getTransitions()` has two optional parameters that we don't currently
support ... `timestamp_begin` and `timestamp_end`. Let's support them now.

Fixes #2479

Reviewed By: @sgolemon

Differential Revision: D1724025

Signature: t1:1724025:1418418358:e4408ada5c240ef13860c777924f8a965b4903c6
typechecker: demand consistent casing for primitive typehints

Summary: ... instead of the baffling behavior of treating `Array` as
 referring to some php-defined class of which the typechecker is unaware.

 As part of this change, consolidate all the errors for the spelling of primitive typehints
 under a single error code

Reviewed By: @paroski

Differential Revision: D1739580

Signature: t1:1739580:1418677499:41984c4b0207686ea7817c219af07c6dcfcc30c5