Include implicit IUSE vars in binhost Packages.

These values may be useful for using a binhost without having a local
copy of the profile (bug #470006).
diff --git a/pym/portage/dbapi/bintree.py b/pym/portage/dbapi/bintree.py
index 7e30208..61ac6b5 100644
--- a/pym/portage/dbapi/bintree.py
+++ b/pym/portage/dbapi/bintree.py
@@ -317,7 +317,9 @@
 				"ACCEPT_KEYWORDS", "ACCEPT_LICENSE",
 				"ACCEPT_PROPERTIES", "ACCEPT_RESTRICT", "CBUILD",
 				"CONFIG_PROTECT", "CONFIG_PROTECT_MASK", "FEATURES",
-				"GENTOO_MIRRORS", "INSTALL_MASK", "USE"])
+				"GENTOO_MIRRORS", "INSTALL_MASK", "IUSE_IMPLICIT", "USE",
+				"USE_EXPAND", "USE_EXPAND_HIDDEN", "USE_EXPAND_IMPLICIT",
+				"USE_EXPAND_UNPREFIXED"])
 			self._pkgindex_default_pkg_data = {
 				"BUILD_TIME"         : "",
 				"DEFINED_PHASES"     : "",
@@ -1259,6 +1261,16 @@
 			else:
 				header.pop(k, None)
 
+		# These values may be useful for using a binhost without
+		# having a local copy of the profile (bug #470006).
+		for k in self.settings.get("USE_EXPAND_IMPLICIT", "").split():
+			k = "USE_EXPAND_VALUES_" + k
+			v = self.settings.get(k)
+			if v:
+				header[k] = v
+			else:
+				header.pop(k, None)
+
 	def _pkgindex_version_supported(self, pkgindex):
 		version = pkgindex.header.get("VERSION")
 		if version: