Restore the implementation of WriteRaw(Stream,string,int) that uses pointers for non-dnx.

StackExchange.Redis/StackExchange/Redis/PhysicalConnection.cs

@@ -603,6 +603,22 @@ unsafe void WriteRaw(Stream stream, string value, int encodedLength)
             }
             else
             {
+#if !DNXCORE50
+                fixed (char* c = value)
+                fixed (byte* b = outScratch)
+                {
+                    int charsRemaining = value.Length, charOffset = 0, bytesWritten;
+                    while (charsRemaining > Scratch_CharsPerBlock)
+                    {
+                        bytesWritten = outEncoder.GetBytes(c + charOffset, Scratch_CharsPerBlock, b, ScratchSize, false);
+                        stream.Write(outScratch, 0, bytesWritten);
+                        charOffset += Scratch_CharsPerBlock;
+                        charsRemaining -= Scratch_CharsPerBlock;
+                    }
+                    bytesWritten = outEncoder.GetBytes(c + charOffset, charsRemaining, b, ScratchSize, true);
+                    if (bytesWritten != 0) stream.Write(outScratch, 0, bytesWritten);
+                }
+#else
                 int charsRemaining = value.Length, charOffset = 0, bytesWritten;
                 var valueCharArray = value.ToCharArray();
                 while (charsRemaining > Scratch_CharsPerBlock)
@@ -614,6 +630,7 @@ unsafe void WriteRaw(Stream stream, string value, int encodedLength)
                 }
                 bytesWritten = outEncoder.GetBytes(valueCharArray, charOffset, charsRemaining, outScratch, 0, true);
                 if (bytesWritten != 0) stream.Write(outScratch, 0, bytesWritten);
+#endif
             }
         }
         const int ScratchSize = 512;