y4m: fix 8bpp build
dct: white-space cleanup
testbench: set g_bitDepth to 10 for HIGH_BIT_DEPTH builds

This more accurately tests our optimized primitives vs the C ref, and several of
them now fail validation.  The intrinsic primitives need to be updated to the
changes made in commit b24d05dd4990 and/or disabled for 16bpp.