Silence 345 sign comparison warnings by iterating with a size_t instead of int.

Very obviously post 0.A.
If this goes out of sync, it is FAR easier to redo than to merge manually, so just poke me about it.
Used these regex in emacs tags-query-replace
```
for( *int *\(.*\) *= *0 *; \1 *< *\(.*\)\.size() *; *\+\+\1 *) / for( size_t \1 = 0; \1 < \2.size(); ++\1 )
for( *int *\(.*\) *= *0 *; \1 *< *\(.*\)\.size() *; *\1\+\+ *) / for( size_t \1 = 0; \1 < \2.size(); ++\1 )
```
I'm sure this could be a one-liner, but I'm not a fan of golf, just getting things done.