Documentation fixes.

modules/juce_core/juce_core.h

@@ -40,6 +40,11 @@ namespace DummyNamespaceStatementToCatchSyntaxErrors {}
     different memory layouts, leading to very nasty memory corruption errors when they all get
     linked together. That's why it's best to always include the Introjucer-generated AppConfig.h
     file before any juce headers.
+
+    Note that if you do have an AppConfig.h file and hit this warning, it means that it doesn't
+    contain the JUCE_MODULE_AVAILABLE_xxx flags, which are necessary for some inter-module
+    functionality to work correctly. In that case, you should either rebuild your AppConfig.h with
+    the latest introjucer, or fix it manually to contain these flags.
  */
  #ifdef _MSC_VER
   #pragma message ("Have you included your AppConfig.h file before including the JUCE headers?")

modules/juce_core/threads/juce_ReadWriteLock.h

@@ -82,8 +82,7 @@ public:
     /** Tries to lock this object for reading.
 
         Multiple threads can simulaneously lock the object for reading, but if another
-        thread has it locked for writing, then this will block until it releases the
-        lock.
+        thread has it locked for writing, then this will fail and return false.
 
         @returns true if the lock is successfully gained.
         @see exitRead, ScopedReadLock