Further reduce the header footprint of Process.h

No functional change here, only deletes unnecessary headers
and moves one function's body from the .h file to the .cpp.

llvm-svn: 231145
diff --git a/lldb/source/Plugins/Process/gdb-remote/ThreadGDBRemote.cpp b/lldb/source/Plugins/Process/gdb-remote/ThreadGDBRemote.cpp
index 5c70cb5..6309f75 100644
--- a/lldb/source/Plugins/Process/gdb-remote/ThreadGDBRemote.cpp
+++ b/lldb/source/Plugins/Process/gdb-remote/ThreadGDBRemote.cpp
@@ -21,6 +21,7 @@
 #include "lldb/Target/StopInfo.h"
 #include "lldb/Target/SystemRuntime.h"
 #include "lldb/Target/Target.h"
+#include "lldb/Target/UnixSignals.h"
 #include "lldb/Target/Unwind.h"
 
 #include "ProcessGDBRemote.h"