* Allow "$" in strings as long as they are not followed by "{". (Too

bad flex doesn't have lexical restrictions, the current solution
  isn't quite right...)

tests/lang/eval-okay-string.exp

@@ -1 +1 @@
-Str("foobar/a/b/c/d/foo/xyzzy/foo.txt/../foo/x/yescape: \"quote\" \n \\end\nof\nlinefoobarblaat")
+Str("foobar/a/b/c/d/foo/xyzzy/foo.txt/../foo/x/yescape: \"quote\" \n \\end\nof\nlinefoobarblaatfoo$bar")

tests/lang/eval-okay-string.nix

@@ -7,3 +7,4 @@
 of
 line"
   + "foo${if true then "b${"a" + "r"}" else "xyzzy"}blaat"
+  + "foo$bar"