internal/pkgbits: sync version.go with goroot

Change-Id: I11d8791a51d7ad5f7d21e71656b3044f5dcd8c8b
Reviewed-on: https://go-review.googlesource.com/c/tools/+/763122
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Mark Freeman <markfreeman@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>

internal/pkgbits/version.go

diff --git a/internal/pkgbits/version.go b/internal/pkgbits/version.go
index 7dc8f4e..0db9652 100644
--- a/internal/pkgbits/version.go
+++ b/internal/pkgbits/version.go
@@ -34,6 +34,9 @@
 	// - a negative struct field index indicates an embedded field
 	V3
 
+	// V4: encodes generic methods as standalone function objects
+	V4
+
 	numVersions = iota
 )
 
@@ -70,6 +73,9 @@
 	// Composite literals use a more compact format for element lists.
 	CompactCompLiterals
 
+	// Generic methods may appear as standalone function objects.
+	GenericMethods
+
 	numFields = iota
 )
 
@@ -78,6 +84,7 @@
 	Flags:               V1,
 	AliasTypeParamNames: V2,
 	CompactCompLiterals: V3,
+	GenericMethods:      V4,
 }
 
 // removed is the version a field was removed in or 0 for fields