Implement central loop as flattend blocks in a switch loop.
Fill out rest of CFG.
Rename transcoding bodies.
Eliminate a level of indirection and go back to Ptr struct.
Fill out remaining required pieces for transcode_restartable0.
More transcoder porting and impl.

* Wire up more transcoder functions correctly.
* Fix minor porting bugs to get a basic transcode to work.
* Add first test for EConv.
Lazily allocate only one char_len holder.
Use a single cached exception for suspend logic.
More minor opto.

* Use ints for state machine to avoid indirection through enums.
* Inline transcoding buffer accessors.
Remove exception flow control logic for suspension.
Hard fail for transcoders that don't impl so/si but need it.
Implement "to" functions for UTF-16 and UTF-32.
More transcoding support for Unicode.

* UTF-16 and UTF-32 should be done now.
* UTF-8-MAC still missing.
* General UTF-8 may be done already.
SO functions for to/from SJIS/EUCJP.
Add TranscodeFunctions.
Add basic tests for EConv.
Reformat code.
Rename some parameters and implement GB18030 functions.
Filling out more transcoder function errors and defaults.
Add easier way to instantiate dummy encodings.