Preps for 1.6.0-rc2 release

Update various version fields.  Also include a note in the release notes
describing Zephyr compatibility.

Signed-off-by: David Brown <david.brown@linaro.org>

README.md

@@ -6,7 +6,7 @@
 [coverity]: https://scan.coverity.com/projects/mcuboot
 [travis]: https://travis-ci.org/JuulLabs-OSS/mcuboot
 
-This is mcuboot version 1.6.0-rc1
+This is mcuboot version 1.6.0-rc2
 
 MCUboot is a secure bootloader for 32-bit MCUs. The goal of MCUboot is to
 define a common infrastructure for the bootloader, system flash layout on

docs/release-notes.md

@@ -32,6 +32,15 @@ updates as well.
   2.9.10 has an infinite loop in a certain end-of-file situation." Fix
   by updating a dependency in documentation generation.
 
+### Zephyr-RTOS Compatibility
+
+This release of MCUboot works the Zephyr "master" at the time of the
+release.  It was tested as of has aff616de20.  When Zephyr v2.3.0 is
+release, there will be a possible 1.6.1 or similar release of Zephyr
+if needed to address any issues.  There also may be branch releases of
+MCUboot specifically for the current version of Zephyr, e.g.
+v1.6.0-zephyr-2.2.1.
+
 ## Version 1.5.0
 
 The 1.5.0 release of MCUboot adds support for encrypted images using

repository.yml

@@ -29,7 +29,7 @@ repo.versions:
     "1.3.1": "v1.3.1"
     "1.4.0": "v1.4.0"
     "1.5.0": "v1.5.0"
-    "1.6.0": "v1.6.0-rc1"
+    "1.6.0": "v1.6.0-rc2"
 
     "0-dev": "0.0.0"        # master
     "0-latest": "1.5.0"     # latest stable release

scripts/imgtool/__init__.py

@@ -12,4 +12,4 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-imgtool_version = "1.6.0rc1"
+imgtool_version = "1.6.0rc2"