Plumb errnum and ExtendedException through the new debugger error hook h...

Summary: ...andler.
Closes https://github.com/facebook/hhvm/pull/3435

Reviewed By: @jlreyes

Differential Revision: D1491840

Pulled By: svcscm
Fix covariance for Const{Vector,Map,Set}, add tests

Reviewed By: @elgenie

Differential Revision: D1499427
Add initial support for -d outside of --php mode

Summary: When we move completely off of HDF and onto ini, we will need native
-d support for hhvm (not just in php emulation mode). This starts that
process. Right now, this should be innocous with respect to HDF, but
should work for the basic case.

Reviewed By: @ptarjan

Differential Revision: D1490638
explicitly use int64_t for seconds in xdebug

Summary: There is no HPHP::StringBuffer::append(time_t). This broke the build on OSX.
Closes https://github.com/facebook/hhvm/pull/3416

Reviewed By: @JoelMarcey

Differential Revision: D1488940

Pulled By: @sgolemon
removed a removeArgs function from the debugger and use the one built into backtrace generation instead

Summary: removed the removeArgs function from cmd_where and had it use the argument to the backtrace generation setting instead.

Reviewed By: @ptarjan

Differential Revision: D1483298