Pull up following revision(s) (requested by christos in ticket #870):

sys/lib/libgnuefi/Makefile.inc: revision 1.5
external/mit/xorg/xorg-pkg-ver.mk: revision 1.9
sys/arch/i386/stand/lib/Makefile.inc: revision 1.17
sys/compat/common/Makefile.inc: revision 1.25
usr.bin/make/unit-tests/varquote.exp: revision 1.1, 1.2
sys/lib/libsa/Makefile.inc: revision 1.24
usr.bin/make/var.c: revision 1.220
sys/arch/ia64/stand/efi/libefi/Makefile.inc: revision 1.5
sys/arch/hppa/spmath/Makefile.inc: revision 1.10
usr.bin/make/unit-tests/varquote.mk: revision 1.1, 1.2
usr.bin/make/unit-tests/Makefile: revision 1.53
sys/lib/libkern/Makefile.inc: revision 1.45
sys/arch/acorn32/stand/lib/Makefile.inc: revision 1.4
sys/arch/m68k/fpsp/Makefile.inc: revision 1.21
usr.bin/make/make.1: revision 1.273
sys/lib/libz/Makefile.inc: revision 1.17

- Introduce :q modifier for make variables and make it double escape $'s so
  that passing variables to recursive makes with :q works as expected.
- Adjust makefiles that use recursive make to use :q

Discussed on tech-toolchain@

XXX: pullup 8

(martin)