package/ci: build also on GCC 4.8.

doc/building.dox

@@ -523,7 +523,7 @@ replace `localhost:8080` with your server name, replace `update-job` with
 
 Build is done using **Ninja** build system and everything possible is enabled,
 thus you need also **SDL2**, **GLUT** and **OpenAL** libraries. It expects
-that **GCC** >= 4.8.1, 4.7 and **Clang** are installed and there
+that **GCC** >= 4.9, 4.8, 4.7 and **Clang** are installed and there
 are **OpenGL**, **OpenGL ES 2.0** and **OpenGL ES 3.0** librares as it tries to
 compile the library with every combination of them. You can add/remove the axes
 in `axes/hudson.matrix.TextAxis` or via the web interface later.

package/ci/jenkins.xml

@@ -53,6 +53,7 @@
       <name>compiler</name>
       <values>
         <string>g++</string>
+        <string>g++-4.8</string>
         <string>g++-4.7</string>
         <string>clang++</string>
         <string>clang++-libc++</string>