Update: add "eoa", add append functions, relocate f_string_dynamic*, and update comments,

Update: add "eoa", add append functions, relocate f_string_dynamic*, and update comments,

"eoa" or "End of Array" is being experimentally added as a compliment of "eos" or "End of String".
Remove stale status code from before I fully embraced error and warning bits.

Add more append functions.
Make existing functions more consistent, checking for array overflows, returning F_array_too_large when appropriate.
Update the comments while I am at it.

Relocate the f_string_dynamic_* functions in string.h and string.c to string-dynamic.h and string-dynamic.c, respectively.
This requires that the string_dynamic.h header depend on string_range.h