The new nether quartz ore block was not recognized and was causing "pillars"
of netherrock to be rendered (with a quartz ore on top). the same
seemed to be happened with Lava, so included taht as well
The nether rendering mode was not properly handling x and z values
outside of the range 0 to 15. This was causing an out-of-bounds
segfault when accessing the remove_block array.
Fixes#881Fixes#851Fixes#852
