reset upstream subtrees to yocto 2.6

Reset the following subtrees on thud HEAD:

  poky: 87e3a9739d
  meta-openembedded: 6094ae18c8
  meta-security: 31dc4e7532
  meta-raspberrypi: a48743dc36
  meta-xilinx: c42016e2e6

Also re-apply backports that didn't make it into thud:
  poky:
    17726d0 systemd-systemctl-native: handle Install wildcards

  meta-openembedded:
    4321a5d libtinyxml2: update to 7.0.1
    042f0a3 libcereal: Add native and nativesdk classes
    e23284f libcereal: Allow empty package
    030e8d4 rsyslog: curl-less build with fmhttp PACKAGECONFIG
    179a1b9 gtest: update to 1.8.1

Squashed OpenBMC subtree compatibility updates:
  meta-aspeed:
    Brad Bishop (1):
          aspeed: add yocto 2.6 compatibility

  meta-ibm:
    Brad Bishop (1):
          ibm: prepare for yocto 2.6

  meta-ingrasys:
    Brad Bishop (1):
          ingrasys: set layer compatibility to yocto 2.6

  meta-openpower:
    Brad Bishop (1):
          openpower: set layer compatibility to yocto 2.6

  meta-phosphor:
    Brad Bishop (3):
          phosphor: set layer compatibility to thud
          phosphor: libgpg-error: drop patches
          phosphor: react to fitimage artifact rename

    Ed Tanous (4):
          Dropbear: upgrade options for latest upgrade
          yocto2.6: update openssl options
          busybox: remove upstream watchdog patch
          systemd: Rebase CONFIG_CGROUP_BPF patch

Change-Id: I7b1fe71cca880d0372a82d94b5fd785323e3a9e7
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/poky/documentation/ref-manual/ref-manual.xml b/poky/documentation/ref-manual/ref-manual.xml
index 9d491e1..f834d2d 100644
--- a/poky/documentation/ref-manual/ref-manual.xml
+++ b/poky/documentation/ref-manual/ref-manual.xml
@@ -123,14 +123,14 @@
                 <revremark>Released with the Yocto Project 2.5 Release.</revremark>
             </revision>
             <revision>
-                <revnumber>2.5.1</revnumber>
-                <date>September 2018</date>
-                <revremark>The initial document released with the Yocto Project 2.5.1 Release.</revremark>
+                <revnumber>2.6</revnumber>
+                <date>November 2018</date>
+                <revremark>Released with the Yocto Project 2.6 Release.</revremark>
             </revision>
             <revision>
-                <revnumber>2.5.2</revnumber>
+                <revnumber>2.6.1</revnumber>
                 <date>&REL_MONTH_YEAR;</date>
-                <revremark>The initial document released with the Yocto Project 2.5.2 Release.</revremark>
+                <revremark>Released with the Yocto Project 2.6.1 Release.</revremark>
             </revision>
         </revhistory>