I fixed following bugs.

I fixed following bugs.
1. In dependency.c, DXE Dispatcher doesn't check the dependency expression boundary correctly.
2. In page.c, a misspelling code in DXE core memory service code, duplicate code.
3. In gcd.c, according to DXE CIS 0-91 spec, When GcdAllocateType is EfiGcdAllocateMaxAddressSearchBottomUp or EfiGcdAllocateMaxAddressSearchTopDown, then the GCD memory space map is searched from the lowest address up to BaseAddress (or from BaseAddress down to the lowest address) looking for unallocated memory ranges of Length bytes. Here, BaseAddress itself is inclusive, that is, any range in [0, BaseAddress] is allowable. But current code BaseAddress to be exclusive.
4. In Ebcinit.c, EbcDebugRegisterPeriodicCallback() not check whether it is already registered.
5. In Ebcinit.c, EbcDebugRegisterExceptionCallback() not check whether it is already registered.
6. In Ebcinit.c, EbcDebugSignalException() does not assign value to EbcContext.ControlFlags.
7. In Ebcinit.c, EBC: StatusCodeValue should use EFI_SOFTWARE_EBC_EXCEPTION.
8. In Ebcinit.c, EbcDebugRegisterExceptionCallback() does not check ExceptionType
9. In ElTorito.c, BlockIo and DiskIo failed in SCT when there is CD in CD-ROM.
10. In Mbr.c, MBR code can't handle some situations. That is when there are 3 partitions in HD, if delete the first partition, it will not be able to recognize the other two partitions, and if delete the second partition, it will not be able to recognize the third partition.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@1749 6f19259b-4bc3-4df7-8a09-765794883524