The basic idea was to reuse the corresponding text space inset in the same
fashion as is already done for references. The dialog displays a different
selection for math than for text. If wanted, the additional spaces could
also be enabled for text, but that would be a file format change.
Constructs like \hspace{\mylengthvariable} that are not supported are
treated by the math parser as ERT as before.
For reasons I don't know the context menu does not work, but this is not so
important IMHO (since a left click opens the dialog).
git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@27954 a592a061-630c-0410-9148-cb99ea01b6c8