This PR includes the following changes that are required to get gRPC to build for ARM/ARM64 on Windows
1) Updated to v1.20.1
2) Disables Codegen Build for ARM/ARM64 builds
3) Rebased the "Fix UWP" patch so that it will apply properly
4) Fixed the "Static Linking in Linux" patch because it specified an invalid option on Windows builds
5) Added patch to "#undef" a macro name collision
6) Added GDI32.lib to the list of standard libraries linked to Windows
