fileset: use fctx.isbinary instead of util.binary(fctx.data())

filectx provides "isbinary" to test if the data is binary. Let's use it.

This enables other filectx implementations (like LFS) to override the
isbinary test.

mercurial/fileset.py

@@ -256,7 +256,7 b' def binary(mctx, x):'
     """
     # i18n: "binary" is a keyword
     getargs(x, 0, 0, _("binary takes no arguments"))
-    return [f for f in mctx.existing() if util.binary(mctx.ctx[f].data())]
+    return [f for f in mctx.existing() if mctx.ctx[f].isbinary()]
 
 @predicate('exec()', callexisting=True)
 def exec_(mctx, x):