Update git submodules

* Update extensions/PdfHandler from branch 'REL1_31'
  to ab596dbb7dc3f162c2772832456a1ad4e6266608
  - Fix for pdfinfo changes in poppler-utils 0.48

    PDF metadata querying was done with pdfinfo's "-meta" and "-l" options
    at the same time, which was supported in poppler 0.26 but not in
    poppler 0.48.

    Upstream change: https://bugs.freedesktop.org/show_bug.cgi?id=96801

    Local change is to run the two as separate commands, then send the
    output together into the existing processing. Should work with older
    poppler-utils on Jessie as well as current one on Stretch.

    Bug: T117839
    Bug: T193200
    Change-Id: Ib4ee9cf12ac04304c576087727eff5dc521ae751

diff --git a/extensions/PdfHandler b/extensions/PdfHandler
index 8d508a9..ab596db 160000 (submodule)
--- a/extensions/PdfHandler
+++ b/extensions/PdfHandler
@@ -1 +1 @@
-Subproject commit 8d508a9c38cc0e81e82518ac88403a95f418e2b2
+Subproject commit ab596dbb7dc3f162c2772832456a1ad4e6266608