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

GDBRemoteCommunicationServer classes. This involved adding a new packet
named "qSpeedTest" which can test the speed of a packet send/response pairs
using a wide variety of send/recv packet sizes.

Added a few new connection classes: one for shared memory, and one for using
mach messages (Apple only). The mach message stuff is experimental and not 
working yet, but added so I don't lose the code. The shared memory stuff
uses pretty standard calls to setup shared memory.

llvm-svn: 128837