dpkg-architecture(1): Document since when DEB_*_MULTIARCH are supported

debian/changelog

@@ -18,6 +18,7 @@ dpkg (1.17.0) UNRELEASED; urgency=low
     - Move EXIT STATUS section before ENVIRONMENT.
     - Rename CAVEATS sections to NOTES.
     - Fold BACKWARD COMPATIBILITY section into other sections.
+    - Document since when DEB_*_MULTIARCH variables are supported.
   * Use colon instead of dot for user:group in dpkg debug output.
   * Remove support for obsolete DM-Upload-Allowed from Dpkg::Vendor::Debian.
   * Fix update-alternatives to use the current alternative link as the first

man/dpkg-architecture.1

@@ -137,7 +137,7 @@ The System part of \s-1DEB_BUILD_GNU_TYPE\s0.
 The \s-1GNU\s0 system type of the build machine.
 .IP "\s-1DEB_BUILD_MULTIARCH\s0" 4
 The clarified \s-1GNU\s0 system type of the build machine, used for filesystem
-paths.
+paths (since dpkg 1.16.0).
 .IP "\s-1DEB_HOST_ARCH\s0" 4
 The Debian architecture of the host machine.
 .IP "\s-1DEB_HOST_ARCH_OS\s0" 4
@@ -156,7 +156,7 @@ The System part of \s-1DEB_HOST_GNU_TYPE\s0.
 The \s-1GNU\s0 system type of the host machine.
 .IP "\s-1DEB_HOST_MULTIARCH\s0" 4
 The clarified \s-1GNU\s0 system type of the host machine, used for filesystem
-paths.
+paths (since dpkg 1.16.0).
 .
 .SH FILES
 .SS Architecture tables