Fix problem with .options file and extension fields.

The options for an extension field were being looked up under wrong name
(MessageName instead of MessageName.fieldname).

Fixed the problem and added regression test. Created a new subfolder for
regression test cases.

Update issue 125
Status: FixedInGit

tests/regression/issue_125/extensionbug.proto

@@ -0,0 +1,16 @@
+message Message1
+{
+	optional uint32	fieldA = 1;
+	extensions 30 to max;
+}
+
+message Message2
+{
+	extend Message1
+	{
+		optional Message2 extras = 30;
+	}
+	
+	optional uint32	field1 = 1;
+	optional uint32 field2 = 2;
+}