build: rename " and "" to quote1 and quote2 for hg

They'll be copied back during installation
but then hg doesn't have to create those files
on systems that have trouble with them.

TBR=rsc
https://codereview.appspot.com/105800043

bin/quote2

@@ -0,0 +1,10 @@
+#!/usr/local/plan9/bin/rc
+
+cmd = `{" $* | tail -1}
+if (~ $#cmd 0) {
+	echo no such command found >[1=2]
+	exit notfound
+}
+
+echo '	' $cmd >[1=2]
+rc -c $"cmd