Refactor the tor_calloc_ overflow check.
Refactor the tor_reallocarray_ overflow check.
Refactor the calloc semantic patch.

This does not change its effects.
The second argument to tor_calloc should be a constant.

Just like the conventional calloc.
Add a rule to the calloc semantic patch for argument ordering.
Remove a duplicate comment.
Document the calloc function overflow check.
Switch to a < comparison for our calloc check; explain how it works
Use the | trick to save a comparison in our calloc check.
Apply new calloc coccinelle patch
Merge branch 'calloc2'
Use tor_malloc_zero(x), not tor_calloc(x,sizeof(char))

(Also, fixes a wide line.)