Define WIN32_LEAN_AND_MEAN globally for win32 builds.

Thanks to Stephen Walker <walk84@yahoo.com> for the patch.
Bug #172898 r=cls a=asa

layout/inspector/src/Makefile.in

@@ -71,7 +71,3 @@ endif
 FORCE_STATIC_LIB = 1
 
 include $(topsrcdir)/config/rules.mk
-
-ifeq ($(OS_ARCH),WINNT)
-DEFINES		+= -DWIN32_LEAN_AND_MEAN
-endif