Rename ProcessBlock to ProcessNewBlock to indicate change of behaviour, and document it

src/main.h

@@ -148,8 +148,16 @@ void RegisterNodeSignals(CNodeSignals& nodeSignals);
 /** Unregister a network node */
 void UnregisterNodeSignals(CNodeSignals& nodeSignals);
 
-/** Process an incoming block */
-bool ProcessBlock(CValidationState &state, CNode* pfrom, CBlock* pblock, CDiskBlockPos *dbp = NULL);
+/** Process an incoming block. This only returns after the best known valid
+    block is made active. Note that it does not, however, guarantee that the
+    specific block passed to it has been checked for validity!
+    @param[out]  state   This may be set to an Error state if any error occurred processing it, including during validation/connection/etc of otherwise unrelated blocks during reorganisation; or it may be set to an Invalid state iff pblock is itself invalid (but this is not guaranteed even when the block is checked). If you want to *possibly* get feedback on whether pblock is valid, you must also install a CValidationInterface - this will have its BlockChecked method called whenever *any* block completes validation.
+    @param[in]   pfrom   The node which we are receiving the block from; it is added to mapBlockSource and may be penalised if the block is invalid.
+    @param[in]   pblock  The block we want to process.
+    @param[out]  dbp     If pblock is stored to disk (or already there), this will be set to its location.
+    @return True if state.IsValid()
+*/
+bool ProcessNewBlock(CValidationState &state, CNode* pfrom, CBlock* pblock, CDiskBlockPos *dbp = NULL);
 /** Check whether enough disk space is available for an incoming block */
 bool CheckDiskSpace(uint64_t nAdditionalBytes = 0);
 /** Open a block file (blk?????.dat) */