parallel sets: fix XML-invalid characters in set names

[LAfricain]

Set names with spaces or other XML-special characters caused a parser error on startup when used as XML tag names (e.g. 'Short set' became <parallel_set_Short set> which is invalid XML).

Fix: automatically convert spaces to underscores when storing set names as XML keys, and convert back for display in the UI.

New helpers in settings.c:
name_to_key(name) - convert display name to XML key (space -> )
key_to_name(key) - convert XML key to display name ( -> space)

Fixes crash on startup when a parallel set name contains a space.

[karlkleinpaste]

FYI I did an adjustment to convert your fprintf to XI_message.

Thanx. This is a very good feature.

[karlkleinpaste]

There is still a problem. This may be a new difficulty since the initial PR, that is, caused by yesterday's fix. I'm not sure.

I have 3 parallel sets defined now.

    <parallel_set_names>Base,Short_set,No_OSHB</parallel_set_names>
    <parallel_set_Base>NET,NETnote,BSB,LXXNA28,ESV,NASB,NIV,NAB,NABnote,KJV,OSHB</parallel_set_Base>
    <parallel_set_current>No OSHB</parallel_set_current>
    <parallel_set_Short_set>NET,BSB,ESV,NASB,NIV</parallel_set_Short_set>
    <parallel_set_No_OSHB>NET,NETnote,BSB,LXXNA28,ESV,NASB,NIV,NAB,NABnote,KJV</parallel_set_No_OSHB>

But I can no longer edit them properly. Changing the pulldown does change which set is displayed for alteration.

In the detached parallel window, I can still select which set to display. But I can't alter those sets now.

[LAfricain]

Ok I'm working on it. If you wouldn't mind, could you check if the other PR is okay and merge it?