Update Crosshatch SVN to 18

Bug:139434268
Change-Id: I5f8af5b0e85747f90962a1b435e6eb1620b5a8ea
(cherry picked from commit 604148aa2d7f664622d5ba3eb2fd73b953a78a1b)
diff --git a/device.mk b/device.mk
index ec07f05..7e79fe8 100644
--- a/device.mk
+++ b/device.mk
@@ -816,7 +816,7 @@
 
 # Increment the SVN for any official public releases
 PRODUCT_PROPERTY_OVERRIDES += \
-    ro.vendor.build.svn=17
+    ro.vendor.build.svn=18
 
 PRODUCT_PRODUCT_PROPERTIES += \
     ro.adb.secure=1