Release numbering

[David Edelsohn]

>>>>> Phil Edwards writes:

Phil> Users expect 3.(x+1) to behave mostly the same as 3.x did.  They will be
Phil> surprised if there are major changes.

Phil> We need to hold the 4.0 label in reserve for Big Incompatible Changes.
Phil> Not just "user-visible" ones, although they clearly would play a part.
Phil> But any change where the users /must/ know whether 3.x or 4.x is in
Phil> use before they (or their tools) can get much farther, /those/ are
Phil> what we should wait for before changing the major version.

	We can change the GCC version to 4.0 the next time libstdc++ is
rewritten or stabilizes, which ever comes first. 1/2 :-)

David