Add .gitattributes

Much nicer for git diff --check.

Change-Id: Id9b757e5ff351181f033c04976edf540cc9c4543

.gitattributes

@@ -0,0 +1,5 @@
+# Disable checks for trailing whitespace for patches, they always trigger warnings,-blank-at-eof
+*.diff whitespace=-trailing-space,-space-before-tab,-blank-at-eof
+*.patch whitespace=-trailing-space,-space-before-tab,-blank-at-eof
+*.exlib whitespace=-blank-at-eof
+*.exheres-0 whitespace=-blank-at-eof