syntax-check: detect incorrect boolean macro values in config.h * modules/maintainer-makefile (configure.ac): Parameterize the location of config.h which will be available to makefiles as $(CONFIG_INCLUDE). The logic is from Eric Blake and the location indicated by Jim Meyering. Note the more natural CONFIG_HEADER name is prohibited by automake for backwards compatibility reasons. * top/maint.mk (sc_Wundef_boolean): New rule.