add jemalloc submodule

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "contrib/jemalloc"]
+	path = contrib/jemalloc
+	url = https://github.com/jemalloc/jemalloc.git

CMakeLists.txt

@@ -13,6 +13,18 @@ endif()
 
 find_package(Git QUIET)
 if(GIT_FOUND AND EXISTS "${PROJECT_SOURCE_DIR}/.git")
+    option(GIT_SUBMODULE "Check submodules during build" ON)
+    if(GIT_SUBMODULE)
+        message(STATUS "Submodule update")
+        execute_process(COMMAND ${GIT_EXECUTABLE} submodule update --init --recursive
+            WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+            RESULT_VARIABLE GIT_SUBMOD_RESULT
+        )
+        if(NOT GIT_SUBMOD_RESULT EQUAL "0")
+            message(FATAL_ERROR "git submodule update --init --recursive failed with ${GIT_SUBMOD_RESULT}, please checkout submodules")
+        endif()
+    endif()
+
     execute_process(COMMAND ${GIT_EXECUTABLE} rev-parse --short HEAD
         WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
         OUTPUT_VARIABLE neo_GIT_REVISION

contrib/jemalloc

@@ -0,0 +1 @@
+Subproject commit ea6b3e973b477b8061e0076bb257dbd7f3faa756