Correctly show MiB symbol instead of MB for GC debug statistics.
For some reason we were converting to MiB (mebibytes) instead of MB (megabytes) even though the output prints "MB".
I keep units of MiB but print out the correct "MiB" symbol now.
I also made a simplification of using
BLOCK_SIZE instead of
BLOCK_SIZE_W = BLOCK_SIZE/sizeof(W_). Concerned about differences in rounding? Assuming
sizeof(W_) is a power of 2 then
BLOCK_SIZE should be divisible by
sizeof(W_). That's certainly true on both 32 and 64 bit systems.