Add ObjC helpers for Any WKT.

- Capture the ObjC prefix used when generating the the file.
- Track the containing type on descriptors.
- Mark descriptors where the message class name got a suffix added to it.
- Expose a fullName property on Descriptors.
- Add helpers for packing/unpacking Any messages.
- Bump the ObjC runtime version number. Since we added methods and invoke them
  in the generated code, ensure the code is running against a matching version.
  Otherwise, someone could compile against headers, but run with a framework
  that is older and get unknown selector failures.  This should trip clearer
  messaging.

Fixes https://github.com/google/protobuf/issues/1674
diff --git a/objectivec/GPBDescriptor.h b/objectivec/GPBDescriptor.h
index 36fb4ea..651f4de 100644
--- a/objectivec/GPBDescriptor.h
+++ b/objectivec/GPBDescriptor.h
@@ -81,6 +81,13 @@
 @property(nonatomic, readonly, getter=isWireFormat) BOOL wireFormat;
 /** The class of this message. */
 @property(nonatomic, readonly) Class messageClass;
+/** Containing message descriptor if this message is nested, or nil otherwise. */
+@property(readonly, nullable) GPBDescriptor *containingType;
+/**
+ * Fully qualified name for this message (package.message). Can be nil if the
+ * value is unable to be computed.
+ */
+@property(readonly, nullable) NSString *fullName;
 
 /**
  * Gets the field for the given number.
@@ -118,6 +125,8 @@
 
 /** The package declared in the proto file. */
 @property(nonatomic, readonly, copy) NSString *package;
+/** The objc prefix declared in the proto file. */
+@property(nonatomic, readonly, copy, nullable) NSString *objcPrefix;
 /** The syntax of the proto file. */
 @property(nonatomic, readonly) GPBFileSyntax syntax;