[Proj] Correction of definition of CRS EPSG 5456 and 5457

[Andre Joost]

Am 28.01.18 um 01:30 schrieb Eduardo Rojas Rodríguez:

> So for me it's a bit strange that this is deprecated and get "better"
> accuracy ???
>

The deprecated transformation 5473 was 7parms without the anchor point. 
This was the reason for the follow-up transformation code 6889 that uses 
Molodensky-Badekas 10parms correctly (but not usable inside PROJ.4).

PROJ.4 first looks at the datum name Ocotepeque 1935 and uses the 
transformation with the largest area of validity. And that is 
transformation 6891 for five countries.

Greetings,
Andre Joost