Compiling chrono generates an inordinate number of warning messages

[DavidHammen]

My bare minimum for a quality C++ software library is that it must compile clean with -Wall using either a GNU or LLVM compiler. The chrono code fails to meet this minimal standard. With -Wall, I get several thousands of lines of warning messages. In fact, the chrono code does not compile clean even without -Wall.

[thepianoboy]

Partially fixed with commit db1ad88
Compiling cleanly with -Wall is somewhat unrealistic for a package with external dependencies like Irrlicht or CUDA. The above commit updates several modules and the core package to build on either GCC or LLVM with typical options and -Werror enabled. This deals with the most common and egregious warnings, and keeps the package clean enough for most open source compiler users. Additional warnings will be addressed in the future, possibly including -Wpedantic to ensure proper cross-compiler compatibility.