FindProtobuf: Search for debug library named with d suffix

Protobuf now provides a CMake-based build system that optionally adds a
suffix to the debug library name [1].  Update our `find_library` call to
consider names with the default value for this suffix, `d`.

[1] https://github.com/google/protobuf/blob/431cee60/cmake/libprotoc.cmake#L107

Modules/FindProtobuf.cmake

@@ -264,7 +264,7 @@ function(_protobuf_find_libraries name filename)
     mark_as_advanced(${name}_LIBRARY_RELEASE)
 
     find_library(${name}_LIBRARY_DEBUG
-      NAMES ${filename}
+      NAMES ${filename}d ${filename}
       PATHS ${Protobuf_SRC_ROOT_FOLDER}/vsprojects/${_PROTOBUF_ARCH_DIR}Debug)
     mark_as_advanced(${name}_LIBRARY_DEBUG)