Mark non-working on NetBSD 5.

Add NetBSD-5 to NOT_FOR_PLATFORM, due to
http://gnats.netbsd.org/46565.  Suggest qemu0 instead.
Fix prototypes. Regenerate patches as unified diffs.
Drop configure flag that no longer exists.
Default arguments during method implementations are nonsense.
Be consistent about using return values.
Don't introduce default arguments during method implementation.
NetBSD/current explicitly needs uvm/uvm_extern.h
Don't add default arguments during method implementation.
Linker flags must be prefixed with -Wl. Don't add default arguments
during method implementation.
Don't add default arguments during method implementation.
Don't include uvm/uvm_object.h, it is for kernel-only use.
If Docbook support is requested and therefore the SAX1 interface, make
sure to include the corresponding source.
Don't add default arguments during method implementation.
Include sys/vmmeter.h and uvm/uvm_extern.h on NetBSD/current.
Include sys/resource.h and uvm/uvm_extern.h for NetBSD/current.
Requires _KMEMUSER as well on NetBSD.
Clean up libXaw handling. [1/2]

- remove LIBXAW variable. It is handled by buildlink3.mk now
- simplify patches and Makefile in packages using libXaw
- in some cases force use of Xaw3d (won't build with Xaw)
- replace some directly included of x11/Xaw3d with mk/xaw.buildlink3.mk

In next part:
- replace more includes with mk/xaw.buildlink3.mk