Strip trailing doc string newline before parsing escape sequences

If the doc string ends on an escaped \r, it should not get eaten
as the "last newline".

lib/PhpParser/ParserAbstract.php

@@ -823,10 +823,10 @@ abstract class ParserAbstract implements Parser {
                         $part->value, $indentLen, $indentChar,
                         $i === 0, $isLast, $part->getAttributes()
                     );
-                    $part->value = String_::parseEscapeSequences($part->value, null, $parseUnicodeEscape);
                     if ($isLast) {
                         $part->value = preg_replace('~(\r\n|\n|\r)\z~', '', $part->value);
                     }
+                    $part->value = String_::parseEscapeSequences($part->value, null, $parseUnicodeEscape);
                     if ('' === $part->value) {
                         continue;
                     }

test/code/parser/scalar/docString.test

@@ -28,6 +28,10 @@ b<<<EOS
 Binary
 EOS;
 
+<<<EOS
+$x\r
+EOS;
+
 -----
 array(
     0: Stmt_Expression(
@@ -112,4 +116,16 @@ array(
             value: Binary
         )
     )
+    7: Stmt_Expression(
+        expr: Scalar_InterpolatedString(
+            parts: array(
+                0: Expr_Variable(
+                    name: x
+                )
+                1: InterpolatedStringPart(
+                    value:
+                )
+            )
+        )
+    )
 )