update PATCHES file

Signed-off-by: Daniel A. Steffen <dsteffen@apple.com>

Author: das

PATCHES

@@ -1,14 +1,21 @@
 The libdispatch project exists in a parallel open source repository at:
-  http://svn.macosforge.org/repository/libdispatch/trunk
+  http://github.com/apple/swift-corelibs-libdispatch
+
+Externally contributed changes are synchronized back to the internal repository
+via pull request of the result of `git am` of the contributed patch series.
 
-Externally committed revisions are periodically synchronized back to the
-internal repository (this repository).
+Internal changes are synchronized from the internal darwin/trunk branch to the
+external repository via `gi am` on the github darwin/trunk branch and merge to
+github master.
 
 Key:
   APPLIED: change set was applied to internal repository.
   INTERNAL: change set originated internally (i.e. already applied).
   SKIPPED: change set was skipped.
 
+svn revisions until r218 from legacy open source repository at
+  http://svn.macosforge.org/repository/libdispatch/trunk
+
 [   1] SKIPPED
 [   2] SKIPPED
 [   3] INTERNAL rdar://problem/7148356
@@ -192,3 +199,15 @@ Key:
 [ 181]
 [ 182]
 [ 183] INTERNAL rdar://problem/7581831
+[ 202] INTERNAL libdispatch-187.5
+[ 212] INTERNAL libdispatch-228.18
+[ 213] INTERNAL rdar://problem/11754320
+[ 216] INTERNAL libdispatch-339.1.9
+[ 217] INTERNAL libdispatch-442.1.4
+[ 218] INTERNAL libdispatch-500.1.5
+
+github commits starting with 29bdc2f from
+
+  http://github.com/apple/swift-corelibs-libdispatch
+
+[29bdc2f] INTERNAL libdispatch-500.1.5