Add LL suffix to avoid c4307

[sloretz]

MSVC will warn with code C4307 and calculate an unintended value if the result of RCUTILS_S_TO_NS is greater than 32bits. As far as I can tell this is because 1000 is small enough to fit in an int so that becomes its type according to https://en.cppreference.com/w/cpp/language/integer_literal . MSVC says the size of int is 4 bytes even on 64bit platforms https://msdn.microsoft.com/en-us/library/s3f49ktz.aspx. In the RCUTILS_S_TO_NS case this means that seconds * 1000 * 1000 * 1000 is done using 32bit math and will overflow when seconds is greater than 2.

[sloretz]

Edit, actually CI isn't crowded right now. Running full CI

* Linux [![Build Status](http://ci.ros2.org/buildStatus/icon?job=ci_linux&build=5169)](http://ci.ros2.org/job/ci_linux/5169/)
* Linux-aarch64 [![Build Status](http://ci.ros2.org/buildStatus/icon?job=ci_linux-aarch64&build=1943)](http://ci.ros2.org/job/ci_linux-aarch64/1943/)
* macOS [![Build Status](http://ci.ros2.org/buildStatus/icon?job=ci_osx&build=4294)](http://ci.ros2.org/job/ci_osx/4294/)
* Windows [![Build Status](http://ci.ros2.org/buildStatus/icon?job=ci_windows&build=5150)](http://ci.ros2.org/job/ci_windows/5150/)