Re-work weight-adjustment code to work in two passes

Re-work weight-adjustment code to work in two passes

It now records how it wants to move each point and them actually moves
the points in a second pass.  This avoids a problem where moving one
point would cause the loop not to correctly recognise the types of
adjacent points in the path.  This in particular affected glyphs with
sharp upper corners (like &) with weights >= 50.