Color any prompt character when there is an error

cmder uses lambda as the prompt character which is a
regular character, so I just removed the test and will
color any random non-whitespace character that is used
in the prompt.

Fixes #180

Author: lzybkr

PSReadLine/Changes.txt

@@ -19,6 +19,7 @@ Bug fixes:
 * Support CancelLine (Ctrl+C) and Abort (Ctrl+G in emacs) to cancel DigitArgument
 * History recall now ignores command lines from other currently running sessions, but you can
   still find command lines from those sessions when searching history.
+* Color any non-whitespace prompt character when there is an error, not just non-characters
 
 New functions:
 * ValidateAndAcceptLine

PSReadLine/Render.cs

@@ -250,14 +250,11 @@ private void ReallyRender()
                         continue;
                     }
 
-                    if (!char.IsLetterOrDigit(c))
-                    {
-                        ConsoleColor prevColor = _consoleBuffer[promptChar].ForegroundColor;
-                        _consoleBuffer[promptChar].ForegroundColor = ConsoleColor.Red;
-                        WriteBufferLines(_consoleBuffer, ref _initialY);
-                        rendered = true;
-                        _consoleBuffer[promptChar].ForegroundColor = prevColor;
-                    }
+                    ConsoleColor prevColor = _consoleBuffer[promptChar].ForegroundColor;
+                    _consoleBuffer[promptChar].ForegroundColor = ConsoleColor.Red;
+                    WriteBufferLines(_consoleBuffer, ref _initialY);
+                    rendered = true;
+                    _consoleBuffer[promptChar].ForegroundColor = prevColor;
                     break;
                 }
             }