Add "to hex" character mappings

[npat-efault]

Consider adding the following character mappings:

• spchex: Map all "special" characters (< 0x20 || 0x7f) to their hexadecimal values, something like this: [17]. Exclude CR, LF and TAB (leave them as is)
• tabhex: Map TAB to its hex value ('[09]')
• crhex: Map CR to its hex value ([0d])
• lfhex: Map LF to its hex value ([0a])
• 8bithex: Map all bytes with the 8th bit set to their hex value
• nrmhex: Map "normal" characters (0x20 <= c < 0x7f ) to their hexadecimal values.

(If more than one mappings apply for a char, then use a predefined mappings precedence order to decide which to apply. Eg: crlf, crhex or crhex, crlf will both map CR -> LF)

[adam-stamand]

Sorry to being this back from the dead, but wouldn't it make sense to have a 'allhex' option so that you can easily get a hexdump of all received characters? I understand you can use several mappings, but I'm not sure you get full coverage with just these mappings.