[PATCH] kconfig: preset config during all*config

Allow to force setting of config variables during all{no,mod,yes,random}config
to a specific value.  For that conf first checks the KCONFIG_ALLCONFIG
environment variable for a file name, otherwise it checks for
all{no,mod,yes,random}.config and all.config.  The file is a normal config
file, which presets the config variables, but they are still subject to normal
dependency checks.

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>