MYNEWT-518 boot - Allow test+confirm as single act

Currently, to permanently run the alternate image, the boot loader
requires the following sequence:

1. image test <slot-01-hash>
2. reboot
3. image confirm

The new feature is to remove the need for the third step. The user
should be able to permanently switch images with this sequence:

1. image confirm <slot-01-hash>
2. reboot
diff --git a/boot/bootutil/test/src/boot_test.h b/boot/bootutil/test/src/boot_test.h
index 072dfbb..d0c1319 100644
--- a/boot/bootutil/test/src/boot_test.h
+++ b/boot/bootutil/test/src/boot_test.h
@@ -67,6 +67,7 @@
                                        int slot);
 void boot_test_util_write_hash(const struct image_header *hdr, int slot);
 void boot_test_util_mark_revert(void);
+void boot_test_util_mark_swap_perm(void);
 void boot_test_util_verify_area(const struct flash_area *area_desc,
                                        const struct image_header *hdr,
                                        uint32_t image_addr, int img_msb);