qpkg: added parsing and recording of Provides data

- pkg.h (enum flags): new flags QPKG_PROVIDED to indicate that the
  package is only a provision, not an installable package
- fixup.h, fixup.c (complete_provisions): search for provisions that do
  not have a real package associated with them, create a package for
  them, and mark it as QPKG_PROVIDED
- qpkg.c (do_fixups): invoke complete_provisions
- pkg.h (struct pkg): add list of (virtual or real) packages a given
  package provides
- pkg.c (new_pkg): initialize pkg->provides
- pkg.c (free_pkg): deallocate pkg->provides
- gobble.c (gobble_buf): parse the list of packages a package provides
- TODO: updated status of Provides support

qpkg/pkg.h

@@ -19,8 +19,9 @@
 
 
 enum flags {
-	/* parse-time flags */
+	/* parse-time and fixup-time flags */
 	QPKG_INSTALLED	= 1 << 0,	/* installed on target */
+	QPKG_PROVIDED	= 1 << 1,	/* virtual package */
 
 	/* run-time flags */
 	QPKG_ADDING	= 1 << 10,	/* resolving dependencies */
@@ -47,6 +48,7 @@ struct pkg {
 	const char *arch;
 	struct ref *conflicts;
 	struct ref *depends;
+	struct ref *provides;
 	const char *filename;
 	int flags;		/* see enum flags */
 	struct pkg *more;