Initial checkin of Pika from heckimp

devel-docs/PIKA3-API-Changes.txt

@@ -0,0 +1,23 @@
+This file contains a list of changes that can/must be done when
+we break API/ABI for 3.x.
+
+
+- Move PIKA_REPEAT_TRUNCATE to the start of the enum and rename it
+  to NONE. Rename the current NONE to EXTEND or something.
+
+- Add LOTS of padding to all public class structs.
+
+- Have private pointers in all public instance structs, not just
+  GET_PRIVATE() macros, in order to inspect the private structs
+  easily in the debugger.
+
+- Remove compat values from all enums.
+
+- Add user_data to all functions passed to pika_widgets_init()
+
+- Preferably make pika_widgets_init() take a vtable with padding.
+
+- Change pika_prop_foo_new() to use the nick as label, or find some
+  other way to use the nick.
+
+- Pass the plug-in protocol version on the plug-in command line.