man: Add version when "new" substvars were introduced in deb-substvars(5)

debian/changelog

@@ -15,6 +15,7 @@ dpkg (1.18.11) UNRELEASED; urgency=medium
     - Add new deb-src-files(5) man page.
       Prompted by Johannes Schauer <josch@debian.org>.
     - Add man page references to other binary control files in dpkg(1).
+    - Add version when "new" substvars were introduced in deb-substvars(5).
   * Build system:
     - Add support for profiling perl modules.
     - Clean up compiler and linker automatic flag usage in configure.

man/deb-substvars.5

@@ -95,15 +95,15 @@ The current host architecture (i.e. the architecture the package is being
 built for, the equivalent of \fBDEB_HOST_ARCH\fP).
 .TP
 .B source:Version
-The source package version.
+The source package version (since dpkg 1.13.19).
 .TP
 .B source:Upstream\-Version
 The upstream source package version, including the Debian version epoch if
-any.
+any (since dpkg 1.13.19).
 .TP
 .B binary:Version
 The binary package version (which may differ from source:Version in a binNMU
-for example).
+for example; since dpkg 1.13.19).
 .TP
 .B Source\-Version
 The source package version (from the changelog file). This variable is now
@@ -158,10 +158,10 @@ Variable settings with names of this form are generated by
 .BR dpkg\-shlibdeps .
 .TP
 .B dpkg:Upstream\-Version
-The upstream version of dpkg.
+The upstream version of dpkg (since dpkg 1.13.19).
 .TP
 .B dpkg:Version
-The full version of dpkg.
+The full version of dpkg (since dpkg 1.13.19).
 .LP
 If a variable is referred to but not defined it generates a warning
 and an empty value is assumed.