sim: add bootstrap test

Add caps for bootstrap option and implement simple bootstrap test
for the simulator.

Signed-off-by: Fabio Utzig <fabio.utzig@nordicsemi.no>
diff --git a/boot/bootutil/include/bootutil/caps.h b/boot/bootutil/include/bootutil/caps.h
index 6f3806e..8ead3be 100644
--- a/boot/bootutil/include/bootutil/caps.h
+++ b/boot/bootutil/include/bootutil/caps.h
@@ -46,6 +46,7 @@
 #define BOOTUTIL_CAP_SWAP_USING_MOVE        (1<<11)
 #define BOOTUTIL_CAP_DOWNGRADE_PREVENTION   (1<<12)
 #define BOOTUTIL_CAP_ENC_X25519             (1<<13)
+#define BOOTUTIL_CAP_BOOTSTRAP              (1<<14)
 
 /*
  * Query the number of images this bootloader is configured for.  This
diff --git a/boot/bootutil/src/caps.c b/boot/bootutil/src/caps.c
index 56b5791..a21bc09 100644
--- a/boot/bootutil/src/caps.c
+++ b/boot/bootutil/src/caps.c
@@ -65,6 +65,9 @@
 #if defined(MCUBOOT_DOWNGRADE_PREVENTION)
     res |= BOOTUTIL_CAP_DOWNGRADE_PREVENTION;
 #endif
+#if defined(MCUBOOT_BOOTSTRAP)
+    res |= BOOTUTIL_CAP_BOOTSTRAP;
+#endif
 
     return res;
 }