Changed CONTEXT into CONTEXT86 everywhere we really want an i386
context.
Added #ifdef __i386__ around accesses to 386 registers in the generic
CONTEXT structure.

diff --git a/msdos/int20.c b/msdos/int20.c
index 4743b74..1ad5b42 100644
--- a/msdos/int20.c
+++ b/msdos/int20.c
@@ -14,7 +14,7 @@
  *
  * Handler for int 20h.
  */
-void WINAPI INT_Int20Handler( CONTEXT *context )
+void WINAPI INT_Int20Handler( CONTEXT86 *context )
 {
         ExitProcess( 0 );
 }