receivingVb was not set when Adapter::Xaction::noteVbContentAvailable was
called.

The bug is probably harmless under most conditions because these simple
adapters are using receivingVb for state checking and the checks seem to work
even if the last assignment is not performed. However, it is impossible to say
for sure.

Index: src/adapter_modifying.cc
===================================================================
--- src/adapter_modifying.cc	(revision 11225)
+++ src/adapter_modifying.cc	(working copy)
@@ -222,7 +222,7 @@
 void Adapter::Xaction::noteVbContentDone(bool atEnd)
 {
 	Must(receivingVb == opOn);
-	receivingVb == opComplete;
+	receivingVb = opComplete;
 	if (sendingAb == opOn) {
 		hostx->noteAbContentDone(atEnd);
 		sendingAb = opComplete;
Index: src/adapter_passthru.cc
===================================================================
--- src/adapter_passthru.cc	(revision 11225)
+++ src/adapter_passthru.cc	(working copy)
@@ -202,7 +202,7 @@
 void Adapter::Xaction::noteVbContentDone(bool atEnd)
 {
 	Must(receivingVb == opOn);
-	receivingVb == opComplete;
+	receivingVb = opComplete;
 	hostx->noteAbContentDone(atEnd);
 }