Release docs: fix notes

We currently do something unusual:  version codes in config.in get
updated after the release, which means that "git describe" won't
match up to development version labels.  Comment that trouble spot.

We can fix this by switching away from the major/minor/micro type
release numbering, as various other projects have done.  The major
numbers basically don't tend to change, and doing a good job with
micro versions is so annoying that they rarely change either.

doc/manual/release.txt

@@ -156,7 +156,8 @@ can be useful when tracking down bugs.
 (Note that at this writing, the tags do not directly
 correspond to <code>git describe</code> output.  The
 hash ID can be used with <code>git show</code>, but
-the preceding segments can't.)
+the relevant repository tag isn't <em>0.3.0-rc1-dev</em>;
+this might change in the future.)
 
 @section releasewho Release Manager
 
@@ -293,17 +294,21 @@ The following steps should be followed to produce each release:
       - If producing the next RC in a series, bump the rc number
     -# Commit that version change.
   -# Create a git tag for the final commit, with a tag name matching
-     the version string in <code>configure.in</code>:
+     the version string in <code>configure.in</code> (including <em>-rcN</em>
+     where relevant):
 @verbatim
 PACKAGE_VERSION="x.y.z"
 PACKAGE_TAG="v${PACKAGE_VERSION}"
 git tag -m "The openocd-${PACKAGE_VERSION} release." "${PACKAGE_TAG}"
 @endverbatim
--# Prepare to resume normal development on mainline:
-  - Restore @c -dev version tag.
-  - To start a new major (or minor) release cycle on the @c master branch:
-    - Archive @c NEWS file as "<code>doc/news/NEWS-${PACKAGE_VERSION}</code>".
-    - Create a new @c NEWS file for the next release
+-# Prepare to resume normal development on mainline (major or minor release)
+  - Update the version label
+     - Restore @c -dev version tag.
+     - For a new minor release cycle, increment the release's minor number
+     - For a new major release cycle, increment the release's major number
+       and zero its minor number
+  - Archive @c NEWS file as "<code>doc/news/NEWS-${PACKAGE_VERSION}</code>".
+  - Create a new @c NEWS file for the next release
   - Commit those changes, and push the commit and the release tag
     to mainline.
 -# Produce the package source archives: