https://gist.github.com/fredemmott/ea681d3acf5fd2fde226 is what's landing for ReflectionParameter shortly.

This logic probably shouldn't be duplicated, but:

- it should be case-insensitive
- hphp_scalar_typehints_enabled() shouldn't be checked here - it changes what the parser emits. Cases are:

1. flag is off, function in hack file. This wil lthen incorrectly say that the parameter isn't a scalar
2. flag is on, function in hack file. All good.
3. flag is on, function in PHP file. All good.
4. flag is off, function in PHP file explicitly typed as 'hh\int'. This should still be considered scalar.