Allow to set a suffix to the Debian package version

Example:
  CPACK_DEBIAN_PACKAGE_VERSION_SUFFIX=+deb8 make deb

Author: Mathieu Parent

CPackConfig.cmake

@@ -1,7 +1,9 @@
 # See http://www.cmake.org/Wiki/CMake:CPackPackageGenerators#Overall_usage_.28common_to_all_generators.29
 
 if(CPACK_GENERATOR MATCHES "DEB")
-    set(CPACK_PACKAGE_FILE_NAME "${CPACK_PACKAGE_NAME}_${CPACK_PACKAGE_VERSION_MAJOR}.${CPACK_PACKAGE_VERSION_MINOR}.${CPACK_PACKAGE_VERSION_PATCH}_${CPACK_DEBIAN_PACKAGE_ARCHITECTURE}")
-    # When the DEB-generator runs, we want him to run our install-script
-    set(CPACK_INSTALL_SCRIPT ${CPACK_DEBIAN_INSTALL_SCRIPT})
+	set(CPACK_DEBIAN_PACKAGE_VERSION_SUFFIX "$ENV{CPACK_DEBIAN_PACKAGE_VERSION_SUFFIX}")
+	set(CPACK_DEBIAN_PACKAGE_VERSION "${CPACK_PACKAGE_VERSION_MAJOR}.${CPACK_PACKAGE_VERSION_MINOR}.${CPACK_PACKAGE_VERSION_PATCH}${CPACK_DEBIAN_PACKAGE_VERSION_SUFFIX}")
+	set(CPACK_PACKAGE_FILE_NAME "${CPACK_PACKAGE_NAME}_${CPACK_DEBIAN_PACKAGE_VERSION}_${CPACK_DEBIAN_PACKAGE_ARCHITECTURE}")
+	# When the DEB-generator runs, we want him to run our install-script
+	set(CPACK_INSTALL_SCRIPT ${CPACK_DEBIAN_INSTALL_SCRIPT})
 endif()

docs/source/installing.rst

@@ -199,4 +199,9 @@ The packages will be created in the build directory.
     `cpack` or `make package`, even on a Unix machine w/ dpkg installed.
     Instead, running `source build.sh` on such a machine will generate a
     Makefile with a separate 'deb' target, so you can run `make deb` to
-    generate the appropriate deb package.
+    generate the appropriate deb package. Additionnaly, you can add a suffix to
+    the package version, for example:
+
+    .. code-block:: bash
+
+        CPACK_DEBIAN_PACKAGE_VERSION_SUFFIX=+deb8 make deb