Minor replace and % funcs improvement.

[seven-phases-max]

I just noticed that the following code:

.test {
    1: replace( "foo", "1", "2");
    2: replace( 'bar', "1", "2");
    3: replace(  baz,  "1", "2");
    4: replace(~"qux", "1", "2");
}

compiles to:

.test {
  1: "foo";
  2: "bar";
  3: "baz";
  4: "qux";
}

So this PR is an attempt to bring some consistency there:

• preserve quote char (", ' or none)
• preserve escaped flag.

[seven-phases-max]

P.S. The same is probably to be done for the % function since it has the same code.
(though I understand that the fact that both functions can accept escaped strings and even tree.Keyword values was unintended and not documented, but if they actually can then...)

[lukeapage]

shall we add tests for this? I'll do this in a couple of days if you don't get round to it

[seven-phases-max]

I can do that. Will it be OK if I also add % changes into this PR?

[lukeapage]

Fine by me.

[seven-phases-max]

Done.