Back to RCPU_CALL for UI8 Linux

Fixes #694, related to #665

src/jit.c

@@ -1137,7 +1137,7 @@ static preg *copy( jit_ctx *ctx, preg *to, preg *from, int size ) {
 				}
 			}
 			if( !is_reg8(from) ) {
-				preg *r = alloc_reg(ctx, RCPU_8BITS);
+				preg *r = alloc_reg(ctx, RCPU_CALL);
 				op32(ctx, MOV, r, from);
 				RUNLOCK(r);
 				op32(ctx,MOV8,to,r);