Local attributes can be used in list of local variables

The syntax for local attributes ('const'/'toclose') was unified with
the regular syntax for local variables, so that we can have variables
with attributes in local definitions with multiple names; for instance:

  local <toclose> f, <const> err = io.open(fname)

This new syntax does not implement constant propagation, yet.

This commit also has some small improvements to the manual.
3 files changed