Revert "[SyntaxColor] Improve highligting of multiline strings"

This reverts commit 86d0fc3.
This was causing a performance regression.

Resolves rdar://problem/32434045

Author: Nathan Hawes

include/swift/IDE/Formatting.h

@@ -81,11 +81,6 @@ class LineRange {
     else if (Line >= StartLine + Length) {
       Length = Line - StartLine + 1;
     }
-    else if (Line < StartLine) {
-      unsigned Delta = StartLine - Line;
-      StartLine -= Delta;
-      Length += Delta;
-    }
   }
 
 };

lib/IDE/SyntaxModel.cpp

@@ -206,13 +206,6 @@ SyntaxModelContext::SyntaxModelContext(SourceFile &SrcFile)
         break;
       }
 
-      case tok::unknown:
-        if (Tok.getText().startswith("\"")) {
-          // invalid string literal
-          Kind = SyntaxNodeKind::String;
-          break;
-        }
-        continue;
       default:
         continue;
       }

test/IDE/coloring.swift

@@ -227,15 +227,6 @@ func f(x: Int) -> Int {
   // CHECK: <str>"This is string </str>\<anchor>(</anchor>genFn({(a:<type>Int</type> -> <type>Int</type>) <kw>in</kw> a})<anchor>)</anchor><str> interpolation"</str>
   "This is string \(genFn({(a:Int -> Int) in a})) interpolation"
 
-  // CHECK: <str>"This is unterminated</str>
-  "This is unterminated
-
-  // CHECK: <str>"This in unterminated with ignored \( "interpolation" ) in it</str>
-  "This in unterminated with ignored \( "interpolation" ) in it
-
-  // CHECK: <str>"This is terminated with \( invalid interpolation" + "in it"</str>
-  "This is terminated with \( invalid interpolation" + "in it"
-
   // CHECK: <str>"""
   // CHECK-NEXT: This is a multiline string.
   // CHECK-NEXT: """</str>
@@ -245,15 +236,9 @@ func f(x: Int) -> Int {
 
   // CHECK: <str>"""
   // CHECK-NEXT: This is a multiline</str>\<anchor>(</anchor> <str>"interpolated"</str> <anchor>)</anchor><str>string
-  // CHECK-NEXT: </str>\<anchor>(</anchor>
-  // CHECK-NEXT: <str>"inner"</str>
-  // CHECK-NEXT: <anchor>)</anchor><str>
   // CHECK-NEXT: """</str>
   """
       This is a multiline\( "interpolated" )string
-   \(
-   "inner"
-   )
    """
 }