[Bf-committers] New Editors menu

[Bastien Montagne]

Hi devs,

The following patch replaces old "manual" Editors menu with nice 
RNA-based one (so once again, some cleanup of old UI code).

http://www.pasteall.org/42945/diff

It makes the following changes:

* Area's type enum still use the same static items, but now has a 
generator func which produces a nice enum mimicking the old all-text 
menu, and without the "EMPTY" entry.

* Two fixes in code drawing enums as dropdown menu:
** All items were taken into account when computing the number of needed 
columns, now simple separators (void string items) are ignored. This 
avoid having two columns in editors menu, but makes sense in general imho!
** Simple separators items were drawn as labels, taking far too much space!

The only change I can see a bit risky is the removal of the 'EMPTY' 
entry in area's type. I made quite a few tests and investigations in 
code, and could not find any issue, but I'd appreciate more experienced 
devs' advices here... ;)

Kind regards,
Bastien