Install THC/THCGeneral.hpp (pytorch#9159)

Summary:
This file was added in pytorch#9107 but wasn't installed. The libraries in
./torch/lib use the headers from Caffe2/ATen from their temporary
install path at torch/lib/tmp_install, and c10d was not able to find
THC/THCGeneral.hpp before this fix.
Closes pytorch#9159

Reviewed By: Yangqing

Differential Revision: D8731107

Pulled By: pietern

fbshipit-source-id: d6009f6f6e8e6e0f37dea24cc4c3570736943ab1

Author: pietern

aten/src/THC/CMakeLists.txt

@@ -59,6 +59,7 @@ set(ATen_CUDA_SRCS ${ATen_CUDA_SRCS}
 INSTALL(FILES
           THC.h
           ${CMAKE_CURRENT_BINARY_DIR}/THCGeneral.h
+          THCGeneral.hpp
           THCBlas.h
           THCSleep.h
           THCStorage.h