Reduce function size in fast & dfast

Reduce function size in fast & dfast

Take the same approach as in PR #2828 [0] to remove functions that force
inline many function bodies and `switch`. Instead, create one function per
"template" combination, and then switch between these functions. This
allows the compiler to break the large function into many small
functions, which generally helps codegen.

Also, in the `extDict` modes when there is no ext-dict, call the top
level function instead of the force inlined one, to save on code size.

I'm specifically doing this because gcc on the parisc architecture doesn't
handle the large function body well, and ends up using a lot of excess
stack space. Outlining these functions fixes it.