Add tools/lsan/suppressions.txt

The new buildbots are using the default config
for ASan, which has Leak Sanitizer (LSan) enabled.
This assumes a suppression file exists in this
location.

TBR=fbarchard@google.com
TESTED=Passing linux_asan trybot run.
BUG=

Review URL: https://webrtc-codereview.appspot.com/27589004

git-svn-id: http://libyuv.googlecode.com/svn/trunk@1091 16f28f9a-4ce2-e073-06de-1de4eb20be90

tools/lsan/suppressions.txt

+# This is a suppressions file that must exist in order for the Leak Sanitizer
+# tool that runs on the ASan bot to be able to run with the default
+# configuration. More info about LSan on
+# http://www.chromium.org/developers/testing/leaksanitizer
+
+#### Third-party leaks ####
+
+#### Actual bugs in Libyuv code ####
+
+