Add Android.mk for CyanogenMod build

I have build this application for CyanogenMod 10-1.

[Release file](https://github.com/illarionov/Android-IMSI-Catcher-Detector/releases/tag/0.1.2.cm-alpha)

There were some problems building this with prebuild framework/telephony libraries, so I used CyanogenMod sources and Android.mk (something like as [SamsungServiceMode app](https://github.com/CyanogenMod/android_packages_apps_SamsungServiceMode)). Maybe this file will be useful for you too.

I have also tested it on Samsung Galaxy S2 (I9100G, radio: I9100GXXLSP)

Log file:
```
I/AIMSICD (  620): Device type   : GSM
I/AIMSICD (  620): Device imei   : imei
I/AIMSICD (  620): Device version: 01
I/AIMSICD (  620): Device num    : 
I/AIMSICD (  620): Network type  : UMTS
I/AIMSICD (  620): Network CellID: XXXX
I/AIMSICD (  620): Network LAC   : 2111
I/AIMSICD (  620): Network code  : 25002
I/AIMSICD (  620): Network name  : MegaFon RUS
```
RIL OEM Hook Text:
Ciphering Indicator - ServiceMode
```
CIPHERING INFO
Is_connected: 0
in_enciphered: 1
Key status: 2
key_context: 2
RAT: 2
```