Add passthrough service manager.

Right now we have logic related to getting passthrough services
generated inside of getService. We should abstract this logic out
into an instance of IServiceManager.

This will:
- abstract passthrough transport implementation from hidl-gen
- decrease code complexity in hidl-gen

Bug: 34394392
Test: hidl_test
Change-Id: Ia6160047c63c6788728d4e17a7cdf67bf6cd06e7
diff --git a/base/HidlSupport.cpp b/base/HidlSupport.cpp
index 5237088..d657793 100644
--- a/base/HidlSupport.cpp
+++ b/base/HidlSupport.cpp
@@ -21,6 +21,7 @@
 
 #ifdef LIBHIDL_TARGET_DEBUGGABLE
 #include <cutils/properties.h>
+#include <dlfcn.h>
 #include <regex>
 #include <utility>
 #endif