How can I exclude unnecessary DLLs from my build?

I’m trying to optimize the file size of my game, in particular the android build. I have optimized the assets and set the build stripping level to Use micro mscorlib. However, looking at the Editor.log reveals the DLLs still take up more than 50%:

Textures      2.7 mb	 35.7% 
Meshes        80.5 kb	 1.0% 
Animations    0.0 kb	 0.0% 
Sounds        0.8 kb	 0.0% 
Shaders       98.2 kb	 1.3% 
Other Assets  177.9 kb	 2.3% 
Levels        110.0 kb	 1.4% 
Scripts       447.4 kb	 5.8% 
Included DLLs 3.9 mb	 52.2% 
File headers  26.2 kb	 0.3% 
Complete size 7.5 mb	 100.0% 

3.9mb seemed a bit much, so I looked at which DLLs are actually added. I found this:

Mono dependencies included in the build
Dependency assembly - Mono.Security.dll
Dependency assembly - System.Core.dll
Dependency assembly - System.dll
Dependency assembly - mscorlib.dll
Dependency assembly - UnityEngine.UI.dll
Dependency assembly - UnityEngine.Networking.dll
Dependency assembly - UnityEngine.Analytics.dll
Dependency assembly - Assembly-CSharp.dll
Dependency assembly - Assembly-UnityScript-firstpass.dll
Dependency assembly - Assembly-UnityScript.dll

This looks like it can be improved quite a bit. I don’t use UnitScript, so Assembly-UnityScript-firstpass.dll and Assembly-UnityScript.dll should be obsolete. Neither do I use Networking or Analytics, so these could be removed as well. Not sure what Mono.Security.dll does or whether UnityEngine.UI.dll is really necessarry.

So, knowing this, how can I get rid of these seemingly unnecessary DLLs?

I asked it in stack overflow: