build: rework verbosity level selection

V=99 and V=1 are now deprecated in favor of a new verbosity class system,
though the old flags are still supported.
You can set the V variable on the command line (or OPENWRT_VERBOSE in the
environment) to one or more of the following characters:

- s: stdout+stderr (equal to the old V=99)
- c: commands (for build systems that suppress commands by default, e.g. kbuild)
- w: warnings/errors only (equal to the old V=1)

SVN-Revision: 31484

include/kernel-defaults.mk

@@ -9,7 +9,8 @@ KERNEL_MAKEOPTS := -C $(LINUX_DIR) \
 	CROSS_COMPILE="$(KERNEL_CROSS)" \
 	ARCH="$(LINUX_KARCH)" \
 	KBUILD_HAVE_NLS=no \
-	CONFIG_SHELL="$(BASH)"
+	CONFIG_SHELL="$(BASH)" \
+	$(if $(findstring c,$(OPENWRT_VERBOSE)),V=1)
 
 ifdef CONFIG_STRIP_KERNEL_EXPORTS
   KERNEL_MAKEOPTS += \
@@ -22,10 +23,6 @@ ifneq (,$(KERNEL_CC))
   KERNEL_MAKEOPTS += CC="$(KERNEL_CC)"
 endif
 
-ifeq ($(KBUILD_VERBOSE),99)
-  KERNEL_MAKEOPTS += V=1
-endif
-
 export HOST_EXTRACFLAGS=-I$(STAGING_DIR_HOST)/include
 
 # defined in quilt.mk