Support ICCIDs containing A-F characters

It seems like there are some carriers who distribute SIM cards using A-F in the ICCID, for example China Mobile (CMCC). Right now the BDC-to-string conversion routines replace those characters with null, which cuts the ICCID short.

This is proper behavior for the spec-compliant case where the only non-BCD character is F, and where it only occurs as padding in 19 character ICCIDs. However, it results in MM reporting a short/incorrect ICCID for these non-spec-compliant cases. QC has suggested a middle ground of ignoring F when it occurs at the end of the BCD string, but otherwise allowing the A-F characters present in the ICCID.

What do you think about this?