Backpatch fixes for Mono to 1.2

Please apply this workaround that David made to the 2.x code to achieve compatibility with Mono.  This will allow those of us stuck with earlier versions of Mono to be able to use SignalR on .NET 4.0.

The embedded Linux/ARMv5 system that I'm coding for has multiple issues with .NET 4.5 on Mono, so SignalR 2.x isn't a possibility on this project. However, .NET 4.0 Mono is solid and SignalR 1.2 works great with the PerformanceCounter exclusion workaround.