Test environments

• Debian Linux, R-devel, GCC ASAN/UBSAN
• Ubuntu Linux 16.04 LTS, R-release, GCC
• win-builder (R-devel and R-release)
• macOS (10.11, 10.14), R-release

R CMD check results

There were no ERRORs or WARNINGs. On some platforms, there is a NOTE about the installed package size.