python: Add patch to avoid warning about bsddb module

_bsddb module can be built only with db version between 4.1 and 4.7.
Avoid a warning by not adding this module to missing variable.

[YOCTO #1937]

(From OE-Core rev: d974ad03c58d7a221ebe3d59c57607928fbbd435)

Signed-off-by: Andrei Gherzan <andrei@gherzan.ro>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/python/python_2.7.2.bb

@@ -1,6 +1,6 @@
 require python.inc
 DEPENDS = "python-native bzip2 db gdbm openssl readline sqlite3 zlib"
-PR = "${INC_PR}.17"
+PR = "${INC_PR}.18"
 
 DISTRO_SRC_URI ?= "file://sitecustomize.py"
 DISTRO_SRC_URI_linuxstdbase = ""
@@ -24,6 +24,7 @@ SRC_URI += "\
   file://setuptweaks.patch \
   file://check-if-target-is-64b-not-host.patch \
   file://search_db_h_in_inc_dirs_and_avoid_warning.patch \
+  file://avoid_warning_about_bsddb.patch \
 "
 
 S = "${WORKDIR}/Python-${PV}"