Move ECM related functions in oscam-ecm.{c,h}

No code changes, just moving ECM functions in single file. oscam-ecm.c
would need some cleanup and probably further splitting but first lets
get the ball rolling by collecting ECM functions in one place.

git-svn-id: http://streamboard.de.vu/svn/oscam/trunk@8242 4b0bc96b-bc66-0410-9d44-ebda105a78c1