README

These are the warning options for the compiler at different levels.

Because GCC produces code which crashes when a function is declared to return a value but doesn't (this is undefined per the C++ specs, but legal for C11 and above code as long as the [non]returned value is ignored), we cannot warn them if we use "-w" to disable all warnings, and instead have to delete every warning but "-Wreturn-type"

Generate the C++ variant with the make_none-cxxflags.sh script

Modify patterns_none-cxxflags.txt patterns to ignore incompatible warning types