splitSFTs.c: fix parsing of misc description field from SFT filenames

Description

• %s is greedy so cannot use as it will just match the rest of the filename; instead use %[^-] to match sequence of characters excluding a hyphen (which separates the 4 basic components S-D-G-T of an SFT filename)
• strtok() doesn't work for parsing misc description fields with underscores; instead use sscanf() with %[] fields to correct match delimiters
• Add test of narrow-banding SFTs one file at a time (new test 1b)

API Changes and Justification

Backwards Compatible Changes

• This change does not modify any class/function/struct/type definitions in a public C header file or any Python class/function definitions
• This change adds new classes/functions/structs/types to a public C header file or Python module

Backwards Incompatible Changes

• This change modifies an existing class/function/struct/type definition in a public C header file or Python module
• This change removes an existing class/function/struct/type from a public C header file or Python module

If any of the Backwards Incompatible check boxes are ticked please provide a justification why this change is necessary and why it needs to be done in a backwards incompatible way.

Review Status

cc @david-keitel