Include C++ header for C string functions.  The header itsself will
have #idndef pragma to prevent duplicate inclusion.  This is fix for
https://github.com/herzi/db2.js/issues/7.  Note that only cstring is
required for bzero, strcmp, and strdup.  cstrings (plural) is not
required.
Merge branch 'master' of https://github.com/jesslilly/db2.js

Conflicts:
	src/connection.cc