This revision can only work with Intel(c) UDK Debugger Tool version 1.3 or greater...

This revision can only work with Intel(c) UDK Debugger Tool version 1.3 or greater. Detailed change log is as below:
1. Add DebugAgentPei driver to initialize Debug Agent in PEI phase.
   Add DebugAgentDxe driver to initialize Debug Agent in DXE phase.
   DebugAgentDxe driver could be loaded and unloaded in shell.
2. Update the SourceLevelDebugPkg so that the debug agent can be initialized in any phase: SEC, PEI or DXE.
3. Add an enhanced retry algorithm that provides a robust connection when data loss happens in the debug channel.
4. Clear DR7 register in exception handler.
5. Set the default serial port parameter to 0 instead of PCDs.
6. Build pointer of Mailbox in HOB instead of Mailbox itself, since HOB may be moved at DXE entry point function.
7. Raise TPL to prevent recursion from EFI timer interrupts in SerialIo.c.
8. Add one spin lock for accessing Mailbox when MP debugging supported.
9. Use more non-NULL library instances in SourceLevelDebugPkg DSC file, thus DebugAgentDxe.efi built from SourceLevelDebugPkg could work in shell.
10.Separate all operations about IDT table entry from SecDebugAgentLib.c into DebugAgent\DebugAgentCommon's arch sub-directory.
11.Enhance Debug Agent to avoid breaking by hardware SMI during DXE debugging phase.
12.Add supporting on mode switch code debugging.
13.Remove reset Host Controller operation in DebugCommunicationLibUsb.c to avoid impacting EDKII usb stack.
14.Fix debug timer interrupt missing issue after back from legacy code.

Signed-off-by: Jeff Fan <jeff.fan@intel.com>
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Signed-off-by: Feng Tian <feng.tian@intel.com>
Reviewed-by: Jeff Fan <jeff.fan@intel.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Feng Tian <feng.tian@intel.com>
git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@14083 6f19259b-4bc3-4df7-8a09-765794883524