[librm] Allow interrupts in protected mode

When running in a virtual machine, switching to real mode may be
expensive.  Allow interrupts to be enabled while in protected mode and
reflected down to the real-mode interrupt handlers.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/x86_64/include/gdbmach.h

@@ -48,4 +48,6 @@ static inline void gdbmach_breakpoint ( void ) {
 
 extern int gdbmach_set_breakpoint ( int type, unsigned long addr, size_t len, int enable );
 
+extern void gdbmach_init ( void );
+
 #endif /* GDBMACH_H */