sanitize system clucene includes

Apparently clucene bundles pieces of a very old version of boost (1.42)
in CLucene/ext/boost, which breaks build with boost 1.54.

Change-Id: Ib244222f8f048aefe0484060f9ad5f41bfd24def

configure.ac

@@ -7376,7 +7376,7 @@ if test "$with_system_clucene" = "yes"; then
     AC_MSG_RESULT([external])
     SYSTEM_CLUCENE=YES
     PKG_CHECK_MODULES(CLUCENE, libclucene-core)
-    CLUCENE_CFLAGS=$(printf '%s' "$CLUCENE_CFLAGS" | sed -e "s/-I/${ISYSTEM?}/g")
+    CLUCENE_CFLAGS=[$(printf '%s' "$CLUCENE_CFLAGS" | sed -e 's@-I[^ ]*/CLucene/ext@@' -e "s/-I/${ISYSTEM?}/g")]
     AC_LANG_PUSH([C++])
     save_CXXFLAGS=$CXXFLAGS
     save_CPPFLAGS=$CPPFLAGS