Reducing iq_buff_size for improved frequency accuracy

[cjb-eng]

The current state of the code appears to have iq_buff_size constrained to a 10 Hz update rate of the code and carrier frequency shifts for the specified receiver sample rate. And 10 Hz rate is limiting the accuracy for high dynamic situations.

It looks like hardcoding of the 10 Hz update rate is isolated to lines 1928-1930, 2212, 2234 in gpssim.c. Can you confirm (or perhaps deny) that the update rate can be modified by adjusting those three sections of code accordingly?

I'm not planning to run this code in a real-time (i.e. w/ SDR) - only produce IQ sample binary files.

[osqzss]

I'm sure the update rate can be modified, but it is hard to tell which lines you have to adjust. I wrote the code a long time ago and can't remember the details.