[x86_64] Fix test failures on 64-bit.

This commit does not actually change the Kiwi.xcodeproj settings to
support 64-bit architectures, it merely fixes test failures that
occur when building for that architecture.

- Fix STAssertEquals failures for mismatched types.
- On 32-bit architectures, `@encode(BOOL)` is equal to "c"; on
  64-bit architectures it is equal to "B". As a result,
  `KWObjCTypeIsNumeric` is no longer true for `BOOL` types. This commit
  adds a `KWObjCTypeIsBool` utility method and allows BOOL values to be
  queried for their `-numberValue` as on 32-bit by modifying
  `KWValue.m`. This fixes failures in the
  `KWBeTrueMatcherTests`, which use `+[KWValue valueWithBOOL:]`.
- Add tests for KWObjCUtilities.