Compilation: Let the code know about package config

This commit adds support for putting package configuration options into
header files. This is needed to prepare reading config files from /etc.

Signed-off-by: Kai Krakow <kai@kaishome.de>

.gitignore

@@ -12,5 +12,6 @@ latex/
 make.log
 make.log.new
 localconf
+lib/configure.h
 scripts/beesd
 scripts/beesd@.service