Enable next_global_mark and prev_global_mark, which works like next_mark and prev_mark, but for global marks, not just local buffer.

[e-loughlin]

Feature Request:

Functions like next_mark and prev_mark, which are currently mapped to '] and '[, respectively. However, these functions only go to the mark within the current buffer.

I'd like the following:

'} -> Go to next global mark (denoted by capital letters, e.g. A goes to B goes to next available...)
'{ -> Go to previous global mark (B to A to Z...)