Improved the packet throughput when debugging with GDB remote by over 3x on

darwin (not sure about other platforms).

Modified the communication and connection classes to not require the
BytesAvailable function. Now the "Read(...)" function has a timeout in
microseconds.

Fixed a lot of assertions that were firing off in certain cases and replaced
them with error output and code that can deal with the assertion case.

llvm-svn: 133224