avutil/version: Improve lib versioning scheme for release branches with the next major release

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavutil/version.h

@@ -41,6 +41,15 @@
  * and its value is reset to 100 instead of 0 to keep it above or equal to 100.
  * Also we do not increase MICRO for every bugfix or change in git master.
  *
+ * Prior to FFmpeg 3.2 point releases did not change any lib version number to
+ * avoid aliassing different git master checkouts.
+ * Starting with FFmpeg 3.2, the released library versions will occupy
+ * a separate MAJOR.MINOR that is not used on the master development branch.
+ * That is if we branch a release of master 55.10.123 we will bump to 55.11.100
+ * for the release and master will continue at 55.12.100 after it. Each new
+ * point release will then bump the MICRO improving the usefulness of the lib
+ * versions.
+ *
  * @{
  */