[gentoo-science] sage-4.3.4 status

[François Bissey]

So we had sage-4.3.4 in the sage-on-gentoo overlay
for a few days already and it has undergone a few changes in that time.

So we are now using system wide sphinx - sphinx is needed
for the help system so you need to have it at runtime.

I added the possibility of building html documentation rather
than downloading it - pdf generation is not yet ready if it will ever be.
To build the doc you need both doc and build-doc useflag.
The option will probably go in the future as it is sloooooow
and the result is slightly different from the official sage documentation
because the sage people patched sphinx to highlight the sage prompt
in the generated documentation. Never mind that it could probably 
be achieved by providing a style sheet or a pygment file.

Other more invisible changes are:
*better separation between DEPEND and RDEPEND.
*added code for a cleaner removal of sage (removal 
of all .pyc and friends).

Francois