The `features` file is converted to a Lua-based DSL.
A helper function `_` is used in the DSL; this will return the original
string for enabled features, and nil for disabled features. This allows
to use boolean operations on features without making the code too
verbose.
Besides having more readable and robust code, this also fixes the bug
that all files `packages/*/features` were evaluated instead of only
using the feature definitions of currently active feeds.
$(TOPDIR) does not contain a trailing slash.
Thus the 'gluon.mk'-include must include
the trailing slash. (Just like the link to
$(INCLUDE_DIR)/package.mk does.)
Signed-off-by: Chris Fiege <chris@tinyhost.de>
