NC: US_LETTER Errors

[Markkos1992]

Listed here:
nc.blueridpkwy   US74A   
nc.us001   US1AFra_N   
nc.us001   US1AFra_S   
nc.us001   US1AWak_N   
nc.us001   US1AWak_S

I really thought that this would be controversial considering that US 1A I believe is still signed that way, but NC 98 using US1Alt instead makes life easy here.

[yakra]

It's been Alt/Bus/Byp instead of A/B since the earliest CHM days, even in states like ME or NY that sign A/B.
Thus A -> Alt in all these examples.

[mapmikey]

changed these and in the queue