Implement first D-specific optimization pass: -simplify-drtcalls. It uses the machinery of the standard -simplify-libcalls pass, but optimizes calls to the D runtime instead of calls to C libraries. At the moment, these optimizations are implemented by this pass: - Avoid the runtime call for `arr.length = newlen` if it can determine that the new length isn't longer than the old one. - Ditto for `cast(T[]) arr` if it will clearly always succeed. (e.g. if the length of the original array is zero, or if the old element size is a multiple of the new element size)

module llvm.va_list;

alias void* va_list;

/*

version(X86)
{
    alias void* va_list;
}
else version(X86_64)
{
    struct X86_64_va_list
    {
        uint gp_offset;
        uint fp_offset;
        void* overflow_arg_area;
        void* reg_save_area;
    }
    alias X86_64_va_list va_list;
}
else
static assert("only x86 and x86-64 support va_list");

*/