Revert "Moved db_drivers/ into external/ for consistency"

This reverts commit b21335642e.

CMakeLists.txt

@@ -159,6 +159,9 @@ link_directories(${UNBOUND_LIBRARY_DIRS})
 # Final setup for rapidjson
 include_directories(external/rapidjson)
 
+
+add_subdirectory(db_drivers)
+
 # Final setup for liblmdb
 include_directories(${LMDB_INCLUDE})
 

external/CMakeLists.txt

@@ -97,5 +97,3 @@ else()
     die("Found libunbound includes, but could not find libunbound library. Please make sure you have installed libunbound or libunbound-dev or the equivalent")
   endif()
 endif()
-
-add_subdirectory(db_drivers)