Support remote GDB debugging.

.gdbinit:
	settings for seamless debugging.

DOC/Debugging.txt:
	add section on how to set up remote debugging.

kernel/Makefile:
	produce a kernel.obj.debug which is relocated to the current kernel
	load address.

util/coff.cpp:
	fix a parameter parsing bug when '-v' was specified;

	reverse-engineered the pei-i386 .stabs section, which will be
	printed with '-v';

	add option '--adjust source <hex>' which will update all code
	references in the .stabs section, as neither GNU objcopy nor LD
	support this properly (at least on cygwin).

	`objcopy --change-addresses 0x13000 --image-base 0x13000 --debugging`
	doesn't do the trick;
	neither does `ld --image-base 0x13000` when given multiple object files,
	nor does explicitly setting the address in the linker file.

vm/vmware/qure-template/qure.vmx:
	add comment-line demonstrating how to enable remote debugging in the VM.