malloc-simple: Make calloc() return zeroed memory

malloc-simple: Make calloc() return zeroed memory

The 0.9.31 release included a change to malloc-simple to request
uninitialized memory from noMMU kernels. Unfortunately, the corresponding
calloc() code assumed that memory returned by malloc() was already zeroed,
which leads to all kinds of nastiness.

Signed-off-by: Steven J. Magnani <steve@digidescorp.com>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>