add 2.7.2 tag changes to NEWS

git-svn-id: https://redoubt.ligo-wa.caltech.edu/svn/advLigoRTS/branches/branch-2.7@3468 6dcd42c9-f523-4c6d-aada-af552506706e

NEWS

 ============================
+Changes for 2.7.2
+============================
+- add utility to remove old IIR filter trends removed in RCG 2.7
+- Zero out the whole EPICS structure in the shared memory.
+  This is needed to make sure all masks are set to zero and
+  all EPICS channels come up unmasked when the code starts.
+============================
 Changes for 2.7.1
 ============================
 - Bug fix (bug 477) - improper generation of DAC monitor screens when both 16bit and 18bit DAC modules