Add an option for controlling the C stack size on Windows.

Add a new option, --cstack-reserve-size, that specifies the amount of virtual
memory that should be reserved for the stack in executables on Windows systems.
This is useful for non-trivial programs that use the high-level C backend since
they often bump into the default 1Mb limit.

compiler/options.m::
	Add the new option.

compiler/compile_target_code.m:
	Pass the appropriate flags to the linker if the new option is given.

doc/user_guide.texi:
	Document the new option.

NEWS:
	Announce the new option.