allow to specify bundle type

[Dirkjan Ochtman]

Benoît Allard wrote:
> My name is on the export, but I have no problem if someone else claims it.

Fixed up versions of these patches are now in c15bfe9cdcd6 (adding 
support for HG10GZ to bundlerepo.bundlerevlog()) and 626cb86a6523 (the 
-t option for bundle). Added some information in the help text, some 
comments in the test code, exec bit for the test code, stuff like that.

Both of these are in crew, I kept your name.

Cheers,

Dirkjan