Always keep the NEWS file from the branch when merging

We usually don't want to touch the NEWS files when we merge and have the
news items not merged by git. Therefore we tell git to use the 'ours' strategy
for the NEWS file.

Author: dsp

.gitattributes

@@ -21,3 +21,4 @@ sapi/nsapi/nsapi.c              ident
 sapi/continuity/capi.c          ident
 Zend/RFCs/002.txt               ident
 Zend/RFCs/003.txt               ident
+NEWS                            merge=ours