Add VGA support on bare metal (#588)

If your main module has this declaration:

    STATIC_YOINK("vga_console");

Then a VGA driver will be linked into your executable which
displays your stdio characters on the PC display, whereas
before we could only use the serial port. Your display is an
ANSI terminal and it's still a work in progress.

examples/hello4.c

@@ -10,6 +10,8 @@
 #include "libc/math.h"
 #include "libc/stdio/stdio.h"
 
+STATIC_YOINK("vga_console");
+
 int main(int argc, char *argv[]) {
   volatile long double x = -.5;
   volatile long double y = 1.5;