man: Move target architecture description to the TERMS section

People expect the terms to be described in the section of the same name,
instead of on some random command-line option.

Closes: #799046

debian/changelog

@@ -1,5 +1,10 @@
 dpkg (1.18.4) UNRELEASED; urgency=low
 
+  [ Guillem Jover ]
+  * Documentation:
+    - Move description for “target architecture” from the dpkg-architecture(1)
+      ‘-A’ option to the TERMS section. Closes: #799046
+
   [ Updated programs translations ]
   * Japanese (Kenshi Muto). Closes: #799432
   * Turkish (Mert Dirik). Closes: #799875

man/dpkg-architecture.1

@@ -103,9 +103,6 @@ Set the host GNU system type.
 .TP
 .BR \-A ", " \-\-target\-arch " \fIarchitecture\fP"
 Set the target Debian architecture (since dpkg 1.17.14).
-This is only needed when building a
-cross-toolchain, one that will be built on the build architecture, to be
-run on the host architecture, and to build code for the target architecture.
 .TP
 .BR \-T ", " \-\-target\-type " \fIgnu-system-type\fP"
 Set the target GNU system type (since dpkg 1.17.14).
@@ -136,6 +133,9 @@ The machine the package is built on.
 The machine the package is built for.
 .IP "target machine" 4
 The machine the compiler is building for.
+This is only needed when building a cross-toolchain, one that will be built
+on the build architecture, to be run on the host architecture, and to build
+code for the target architecture.
 .IP "Debian architecture" 4
 The Debian architecture string, which specifies the binary tree in the
 FTP archive. Examples: i386, sparc, hurd\-i386.