fixes for compiling with gcc 10

gcc 10 no longer lets you get away with not externing global variables in header files. This adds the necessary extern and adds defines in appropriate c files

bootloader/gfx/gfx.c

@@ -19,6 +19,10 @@
 #include <string.h>
 #include "gfx.h"
 
+// Global gfx console and context.
+gfx_ctxt_t gfx_ctxt;
+gfx_con_t gfx_con;
+
 static const u8 _gfx_font[] = {
 	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // Char 032 ( )
 	0x00, 0x30, 0x30, 0x18, 0x18, 0x00, 0x0C, 0x00, // Char 033 (!)