Patch a asterisk module without breaking package management on Ubuntu

I needed to modify one module (chan_sip) of Asterisk, but was to lazy to download and install Asterisk manually.

1. Install build-tools
   apt-get install build-essential
2. Get the source and build dependencies
   apt-get source asterisk
   apt-get build-dep asterisk
3. Patch or do whatever you wanted.
   ....
4. Re-compile Asterisk
   ./configure && make
5. Install the Asterisk module
   cp channels/chan_sip.so /usr/lib/asterisk/modules/

PS: Was done on Ubuntu 13.10.