[GRASS5] Let's publish 5.0.3

[Markus Neteler]

Dear developers

I feel that we should release quickly 5.0.3 and
prepare 5.3.0 as well.

First we have to decide which changes should reach
the 5.0.3 version (a.k.a. current release branch).

for that please make use of:
tools/diff.sh
and update missing changes in the release branch
(but only those which should go into 5.0.3:  
HTML fixes and other minor fixes).

The further procedure might be:
- release 5.0.3 soonish
- rename 5.1.0 to 5.7.0
- open a new 5.3.0 release branch (with NVIZ updates, proj updates etc)
- start 5.3.0 testing
etc.

Compare also
http://grass.itc.it/roadmap.html

Markus