deb-symbols(5): Document that the main-dependency-template is always used

The main-dependency-template always gets added, and might end up being
combined with the template pointed by id-of-dependency-template if that
is present.

Closes: #737731

debian/changelog

@@ -1,5 +1,10 @@
 dpkg (1.17.7) UNRELEASED; urgency=low
 
+  [ Guillem Jover ]
+  * Documentation:
+    - Mention in deb-symbols(5), that the “main-dependency-template” is
+      always used. Closes: #737731
+
   [ Updated dpkg translations ]
   * German (Sven Joachim).
   * Swedish (Peter Krefting).

man/deb-symbols.5

@@ -46,7 +46,8 @@ an unversioned dependency is deemed sufficient).
 Each exported \fIsymbol\fR (listed as \fIname\fR@\fIversion\fR, with
 \fIversion\fR being "Base" if the library is not versioned) is associated
 to a \fIminimal-version\fR of its dependency template (the main dependency
-template is used if \fIid-of-dependency-template\fR is not present). The
+template is always used and will end up being combined with the dependency
+template referenced by \fIid-of-dependency-template\fR if present). The
 first alternative dependency template is numbered 1, the second one 2,
 etc.
 .P