Add reallocarray clone so we can stop doing multiply-then-reallocate
Add a simple coccinelle script to replace malloc->calloc

Coccinelle is a semantic patching tool that can automatically change
C code via semantic patching.

This script also replaces realloc with reallocarray as appropriate.
Apply coccinelle script to replace malloc(a*b)->calloc(a,b)
Add changes file for bug12855
Fix whitespace issues
Merge remote-tracking branch 'public/use_calloc'