mq: remove unused repo._committingpatch-related code

This was introduced in 20ad8f0512a2 but its usage was removed in
46cc3b74e1c5.
util.h: fix gcc version checking

gcc doesn't have a predefined GCC_VERSION macro.
hgweb: show a message when there are no more entries in the list
hgweb: show loading indicator while an ajax request is in process
hgweb: show message when an error occured during ajax loading
commands: import hgweb.server in a way that 2to3 can rewrite
run-tests: if run by python3, execute setup.py with --c2to3
run-tests: find mercurial path with syntax valid on both py2 and py3
hgweb: add CSS class to the last entry on a page

The entry which was last before an ajax load now has a specific CSS class
for easier styling.
paper: add simple animation to the loading indicator
paper: add reddish background to ajax error message
strip: set current bookmark to None if stripped

--HG--
branch : stable
merge with stable