- use <xxx.h> instead of <cxxx> (e.g. use stdlib.h instead of cstdlib)
- avoid using variable length array
as for the first point, it didn't make sense that cxxx didn't work and we may
want to look into it further to understand the real cause.  but since this has
been breaking build, and it somehow fixes the issue, I'll apply it for now.

okayed on jabber.