Add the external/jemalloc project.

default.xml

@@ -145,6 +145,7 @@
   <project path="external/javasqlite" name="platform/external/javasqlite" />
   <project path="external/javassist" name="platform/external/javassist" />
   <project path="external/jdiff" name="platform/external/jdiff" />
+  <project path="external/jemalloc" name="platform/external/jemalloc" />
   <project path="external/jhead" name="platform/external/jhead" groups="pdk" />
   <project path="external/jmdns" name="platform/external/jmdns" />
   <project path="external/jmonkeyengine" name="platform/external/jmonkeyengine" />