Plantlike: Fix visual_scale being applied squared

Plantlike: Fix visual_scale being applied squared

This re-applies 2 commits that were reverted.

Visual_scale was applied twice to plantlike by accident sometime between
2011 and 2013, squaring the requested scale value. Visual_scale is
correctly applied once in it's other uses in signlike and torchlike.

Two lines of code are removed, they also had no effect for the vast
majority of nodes with the default visual_scale of 1.0.
The texture continues to have it's base at ground level.

Send sqrt(visual_scale) to old clients.

Keep compatibility with protocol < 30 clients now that visual_scale
is no longer applied twice to plantlike drawtype and mods are being
updated to a new value.