Move compiler.h to commonlib

Its spreading copies got out of sync. And as it is not a standard header
but used in commonlib code, it belongs into commonlib. While we are at
it, always include it via GCC's `-include` switch.

Some Windows and BSD quirk handling went into the util copies. We always
guard from redefinitions now to prevent further issues.

Change-Id: I850414e6db1d799dce71ff2dc044e6a000ad2552
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/28927
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

util/cbmem/Makefile

@@ -21,6 +21,7 @@ PREFIX   ?= /usr/local
 CFLAGS   ?= -O2
 CFLAGS   += -Wall -Werror
 CPPFLAGS += -I . -I $(ROOT)/commonlib/include
+CPPFLAGS += -include ../../src/commonlib/include/commonlib/compiler.h
 
 OBJS = $(PROGRAM).o