Enable aggressive static analysis flags - resolve resulting issues

[kscz]

Enable -Wall -Wextra and -Werror (as well as a few more useful lints) and then fix everything to get it compiling.

• The snprintf statements in mm_carrier.c and mm_carrier_mtrl.c seem to leave a space for the null terminator, but snprintf guarantees a null terminator, so you will get truncation!
• A number of places had for loops with int i but were compared against the output of sizeof - switched them to size_t i
• There were a number of places which used %llx, %lld, and %llu to print out uint64_t or int64_t types - switch these to their standard PRIx64, PRId64, and PRIu64 counterparts
• Add in a few missing function prototypes
• Remove const from some functions which claimed their return type was const, which didn't make sense since the functions returned basic types by copy

[kscz]

Ended up disabling the flags in the final build, but figured the code cleanup couldn't hurt. I think it would have worked for both Mac and Linux, but the windows build failures were mysterious flag issues which I was not inclined to repair.

It looks like the windows build is now failing due to the fact that I don't have permission for something - could you please attempt to re-kick it off @hharte ?

Thanks! And let me know if you'd prefer me to change anything!

[hharte]

Thank you!