Punt in ARM codegen for CallBuiltin if it needs stack args

Summary: They're not yet supported. I put the punt here rather than in
cgCallHelper itself because cgCallHelper is sometimes called in places that
can't handle punting.

Reviewed By: @edwinsmith

Differential Revision: D1577753
Refactor the parsing and processing of config options

Summary: The rise from the ashes edition....

D1554807 reverted the refactoring that I did to prepare for the hdf move to ini conversion because, well, I had missed a couple of things and started to break stuff.

Here we go, trying this again. I think we are at equivalent functionality as before this diff, modulo some bug fixes that should be useful and good.

Here is the lowdown:

1. Refactor so we have one goto place for parsing, processing and binding of config options.
2. Fixed a bug where some `-v` overrides were not being respected when the same option was being given in a `.ini` file.
3. Fixed a bug in `IniSetting::Set` where updates were not happening to existing pairs. That was actually a subtle, but big find.
4. Got a little more clever on how we re-parsed ini files for extension constants. Before we were parsing the whole file again, un-overriding any overrides that were given at the command line. Now we just deal with unbounded extension constants.
5. Precendence order for config options should be right. `ini file -> hdf file -> ini cli settings -> hdf cli settings -> Tiers -> ini cli settings re-check -> hdf cli settings re-check -> Load and Bind`
6. Reflect reality when it comes to the actual value of a `RuntimeOption` compared to the value exposed to a call to `ini_get()` for that `RuntimeOption`.
7. In the short term, during the migration, hdf always wins over ini.

Reviewed By: @markw65

Differential Revision: D1555790