Remove unused NativeProcessProtocol.h include from Platform.h

After removing it, I got a couple of compile errors because we were
missing some symbols (SIGKILL and such), as their definitions were not
transitively included anymore. I fix this by including csignal from
PosixApi.h, as it's windows version provides a stub definitions of these
symbols. This should make the result of #including PosixApi.h more
consistent across platforms (although in the long run, we should just
get rid of this header).

llvm-svn: 329296

lldb/include/lldb/Host/PosixApi.h

@@ -18,6 +18,7 @@
 #include "lldb/Host/windows/PosixApi.h"
 #else
 #include <unistd.h>
+#include <csignal>
 #endif
 
 #endif

lldb/include/lldb/Target/Platform.h

@@ -30,10 +30,6 @@
 #include "lldb/lldb-private-forward.h"
 #include "lldb/lldb-public.h"
 
-// TODO pull NativeDelegate class out of NativeProcessProtocol so we
-// can just forward ref the NativeDelegate rather than include it here.
-#include "lldb/Host/common/NativeProcessProtocol.h"
-
 namespace lldb_private {
 
 class ModuleCache;