Lighttpd

The attached patch fixes three things:

 - the logic of all the optional features (AC_ARG_WITH stuff)
 - FAM_LIB should be FAM_LIBS (pkg-config sets VAR_LIBS and VAR_CFLAGS).
    Also the AC_SUBST is unnecessary as PKG_CHECK_MODULES automatically
   calls AC_SUBST for VAR_LIBS and VAR_CFLAGS iirc.
 - typos in the (en|dis)able_features stuff.  Both gdbm and memcache
   conditonionals set enable_features even if disabled, thus they show up
   as enabled even when they're not.

The first item required a little more explanation as to why the current logic
is flawed. The current logic assumes that if --with-OPTION is specified
that it should be enabled. This goes out the window as soon as a user
specifies --without-OPTION (which autoconf interprets as --with-OPTION=no).
As I explained on irc, this breaks build systems that automatically pass
--with-OPTION or --without-OPTION based on whether the OPTION flag is set
(gentoo calls them USE flags).

-- ka0ttic