Audit malloc(3)/calloc(3)/realloc(3) usage.

Audit malloc(3)/calloc(3)/realloc(3) usage.
* Change eight reallocs to reallocarray to be safe from overflows.
* Change one malloc to reallocarray to be safe from overflows.
* Change one calloc to reallocarray, no zeroing needed.
* Change the order of arguments of three callocs (aesthetical).