Allow virtuals in package.provided

With new-style virtuals, there is no reason to enforce special rules to
virtuals in package.provided. If user wishes to implicitly provide
the virual package, we should not forbid him. Of course, he knows
the implications.

This is upstream commit e3366b392c76249ead2ef947b275eb5bba99bc1e.

BUG=24614250
TEST=added virtual/libc-0 to package.provided and it worked

Change-Id: Iddb17763b62eed6087c8f954568167d4078330b7
diff --git a/usr/lib/portage/pym/portage/package/ebuild/config.py b/usr/lib/portage/pym/portage/package/ebuild/config.py
index f3633ed..08f048f 100644
--- a/usr/lib/portage/pym/portage/package/ebuild/config.py
+++ b/usr/lib/portage/pym/portage/package/ebuild/config.py
@@ -782,12 +782,6 @@
 					has_invalid_data = True
 					del pkgprovidedlines[x]
 					continue
-				if cpvr[0] == "virtual":
-					writemsg(_("Virtual package in package.provided: %s\n") % \
-						myline, noiselevel=-1)
-					has_invalid_data = True
-					del pkgprovidedlines[x]
-					continue
 			if has_invalid_data:
 				writemsg(_("See portage(5) for correct package.provided usage.\n"),
 					noiselevel=-1)