Include the scan-build.sh script I used for 8793

Otherwise we'll never remember what to re-run before each release, or
whether we tried a given checker.

contrib/scan-build.sh

+#!/bin/sh
+# Copyright 2014 The Tor Project, Inc
+# See LICENSE for licensing information
+#
+# This script is used for running a bunch of clang scan-build checkers
+# on Tor.  
+#
+# It has hardwired paths for Nick's desktop at the moment.
+
+CHECKERS="\
+    --use-analyzer=/opt/clang-3.4/bin/clang \
+    -disable-checker deadcode.DeadStores \
+    -enable-checker alpha.core.CastSize \
+    -enable-checker alpha.core.CastToStruct \
+    -enable-checker alpha.core.IdenticalExpr \
+    -enable-checker alpha.core.SizeofPtr \
+    -enable-checker alpha.security.ArrayBoundV2 \
+    -enable-checker alpha.security.MallocOverflow \
+    -enable-checker alpha.security.ReturnPtrRange \
+    -enable-checker alpha.unix.SimpleStream
+    -enable-checker alpha.unix.cstring.BufferOverlap \
+    -enable-checker alpha.unix.cstring.NotNullTerminated \
+    -enable-checker alpha.unix.cstring.OutOfBounds \
+    -enable-checker alpha.core.FixedAddr \
+    -enable-checker security.insecureAPI.strcpy
+"
+
+/opt/clang-3.4/bin/scan-build/scan-build \
+    $CHECKERS \
+    --use-analyzer=/opt/clang-3.4/bin/clang \
+    ./configure
+
+/opt/clang-3.4/bin/scan-build/scan-build \
+    $CHECKERS \
+    --use-analyzer=/opt/clang-3.4/bin/clang \
+    make -j2
+
+
+# Haven't tried this yet.
+#    -enable-checker alpha.unix.PthreadLock
+
+# This one gives a false positive on every strcmp.
+#    -enable-checker alpha.core.PointerSub
+
+# This one hates it when we stick a nonzero const in a pointer.
+#    -enable-checker alpha.core.FixedAddr
+
+# This one crashes sometimes for me.
+#    -enable-checker alpha.deadcode.IdempotentOperations