New global bindings

[Stefan Monnier]

I have some problems with the new global bindings for C--, C-=, and C-+:
1- they're not mentioned in etc/NEWS (it seems none of the face-remap
    feature is mentioned there).
2- (control -) was used for negative prefix arguments, so this is
    a significant change for oldtimers.
3- these are very short key-bindings for a feature that does not seem to
   require them: you're unlikely to want to do it that frequently.

Point nb 1 is easy to fix, maybe I can live with nb 3, but nb 2 seems to
be more problematic.  So I think we need to find some other key-bindings
for that.  I think a prefix key followed by +, -, and = (repeatable like
C-x e e e e e, maybe even allowing switching between + and -) is the
best choice.


        Stefan