1) A new macro YAML_CPP_NORETURN to annotate functions as not returning in dll.h
2) A new function YAML_throw<ExceptionType>(args...) in exception.h
this function will throw an exception unless exceptions are disabled in the compiler,
detected by checking the pre-defined macro __cpp_exceptions
In this case the exception class will be instantiated, and the user-provided function
YAML::handle_exception(const char*) will be called on the exception's what() method
3) if exceptions are disabled,and the library's user does not provide YAML::handle_exception,
there will be a linker error
4) all other files have been changed automatedly by running the following sed commands
sed -i "s/throw \([A-Za-z]*\)(\(.*\))/YAML_throw<\1>(\2)/g" # throw statements for non-templated exceptions
sed -i "s/throw \(.*\)<\(.*\)>(/YAML_throw<\1<\2> >(/g" # throw statements for templated exceptions
