Explicitly include stdarg.h pulled in by namespace-protected sqlite.h.

The namespace wrapper around sqlite.h forces the va_list type definition into the same namespace. A latter include of <cstdarg> may therefore break as seen with libc++.
Merge pull request #172 from jsonn/patch-1

Explicitly include stdarg.h pulled in by namespace-protected sqlite.h.
Replace stdarg.h with cstdarg
Merge branch 'develop' into hotfix/3.2.2