Adds advice to use correct variant of the developer command prompt for x64 build target (#201)
Adds advice to use correct variant of the developer command prompt for x64 build target (#201)

Using the default Visual Studio Developer Command Prompt will fail to build with linker errors if using the x64 version of Postgres as the source. To build successfully using the x64 version of Postgres source your must run the ```nmake``` command under the "x64 Native Tools Command Prompt" instead.
jtv/libpqxx,jtv/libpqxx,jtv/libpqxx,jtv/libpqxx