Work in progress. Fix some thread handling problems.

src/e-server:
	* src/GdbServer.cpp (GdbServer::rspClientRequest): Pass core ID to
	targetResume, call new function rspIsThreadAlive for 'T' packet.
	(GdbServer::rspContinue): Pass core ID to getException.
	(GdbServer::targetResume): Take core ID as argument, and pass when
	resuming or testing for halt.
	(GdbServer::rspSuspend): Simplified handling of exception signals,
	pass core ID when resuming.
	(GdbServer::redirectSdioOnTrap): Pass core ID when resuming.
	(GdbServer::rspStep): Signal argument is of type TargetSignal,
	rewrite for simplification and clarity.
	(GdbServer::rspIsThreadAlive): Created.
	(GdbServer::targetHalt): Pass CoreID to when halting and testing
	for halt. Consistent trace messaging.
	(GdbServer::insertBkptInstr): Renamed from
	putBreakPointInstruction, cleaner trace message.
	(GdbServer::isCoreHalted): rename from IsTargetInDebugState, take
	coreID as argument and use when reading reg.
	(GdbServer::isTargetExceptionState): Replaced by getException.
	(GdbServer::getException): Rewrite of isTargetExceptionState to
	take core ID as argument and return signal.
	(GdbServer::saveIVT): Take core ID as argument and use when
	reading memory.
	(GdbServer::restoreIVT): Take core ID as argument and use when
	writing memory.
	(GdbServer::rspVpkt): Return S05 for attach.
	(GdbServer::rspInsertMatchpoint): Rename putBreakPointInstruction
	as insertBkptInstr.
	(GdbServer::cCore): Deal with 0 and -1 as threads
	(GdbServer::gCore): Likewise.
	(GdbServer::getOpcode1_4): Created.
	(GdbServer::getOpcode1_5): Created.
	(GdbServer::getOpcode2_4): Created.
	(GdbServer::getOpcode4): Created.
	(GdbServer::getOpcode4_2_4): Created.
	(GdbServer::getOpcode4_5): Created.
	(GdbServer::getOpcode4_7): Created.
	(GdbServer::getOpcode4_10): Created.
	(GdbServer::getOpcode5): Created.
	(GdbServer::getOpcode7): Created.
	(GdbServer::getOpcode10): Created.
	(GdbServer::getRd): Created.
	(GdbServer::getRm): Created.
	(GdbServer::getRn): Created.
	(GdbServer::getTrap): Created.
	(GdbServer::getBranchOffset): Created.
	(GdbServer::getJump): Created.
	* src/GdbServer.h: Remove SPECIAL_INSTR_OPCODES and add IDLE_INSTR
	as constant.  Change rspStep prototypes to use TargetSignal for
	exceptions. Rename putBreakPointInstruction as insertBkptInstr.
	Replace isTargetExceptionState by getException.  Pass core ID to
	isCoreHalted, getException, saveIVT, restoreIVT.  Add declarations
	of instruction field access methods.
	* src/RspConnection.cpp (RspConnection::getBreakCommand): Remove
	warning messave if signal interrupts read. Always return bool as result.
	* src/TargetControl.h: Add status exception causes.
	* src/TargetControlHardware.cpp (TargetControlHardware::writeMem8):
	(TargetControlHardware::readMem): Rewritten for clarity. Pass
	coreID when converting address.
	(TargetControlHardware::writeMem): Likewise.
	(TargetControlHardware::readBurst): Likewise.
	(TargetControlHardware::writeBurst): Likewise.
	(TargetControlHardware::writeTo): Better trace message.
	* src/TargetControlHardware.h: Change size constants and
	parameters to type size_t consistently.