[Locale] Added stubs as a replacement for the intl extension

You can enable the stubs by including the following code in app/autoload.php:

$loader->registerPrefixFallback(array(
    __DIR__.'/../vendor/symfony/src/Symfony/Component/Locale/Resources/stubs',
));

If the intl extension is not loaded, the stub classes for the "en" locale
will be created automatically.
[Locale] first implementation of StubIntlDateFormatter
[Locale] add support for escaping, give specifics on implementation used in tests
[Locale] move intl bugs to skipped tests
[Locale] support for G and Q placeholders in StubIntlDateFormatter::format
[Locale] add support for L, which is the same as M
[Locale] use assertSame instead of assertEquals
[Locale] add support for h
[Locale] support for D (day of year)
[Locale] support for E (day of week)
[Locale] support for a (AM/PM)
[Locale] support for H (24 hour)
[Locale] refactor IntlDateFormatter::format to build regExp dynamically
[Locale] implement k (24-hour (1-24)
[Locale] support for K (12-hour (0-11))
[Locale] support for m (minute of hour)
[Locale] support for s (second)
[Locale] refactor to use DateTime and DateTimeZone, adding timezone support
[Locale] support for z (timezone offset from GMT)
[Locale] add a list of unimplemented date format keywords