* Make a difficult mutex check a bit easier to read and hopefully a b…

…it safer, too

* Reorder some code
* Replace some duplicate code with goto
* Simplify some if's

Maybe this also has some influence on our current top crash ("Attempted to connect a connection that is not disconnected")

Source/SPConstants.h

@@ -682,3 +682,12 @@ typedef NSUInteger NSCellHitResult;
 
 // See http://stackoverflow.com/questions/4415524
 #define COUNT_OF(x) ((sizeof(x)/sizeof(0[x])) / ((size_t)(!(sizeof(x) % sizeof(0[x])))))
+
+// This definition is mostly for legibility
+#ifndef ESUCCESS
+	#define ESUCCESS 0
+#else
+	#if ESUCCESS != 0
+		#error 'ESUCCESS' must be defined as zero!
+	#endif
+#endif

Source/SPDatabaseStructure.h

@@ -51,7 +51,6 @@
 // Setup and teardown
 - (id)initWithDelegate:(SPDatabaseDocument *)theDelegate;
 - (void)setConnectionToClone:(SPMySQLConnection *)aConnection;
-- (void)destroy:(NSNotification *)notification;
 
 // Information
 - (SPMySQLConnection *)connection;