Add USAGE_SHARED to driver.

Change-Id: Ie04f8ee2d6080729660dbe82b3a09af5cd40e239
diff --git a/rsDefines.h b/rsDefines.h
index 8900c13..b1f1041 100644
--- a/rsDefines.h
+++ b/rsDefines.h
@@ -106,6 +106,7 @@
     RS_ALLOCATION_USAGE_GRAPHICS_RENDER_TARGET = 0x0010,
     RS_ALLOCATION_USAGE_IO_INPUT = 0x0020,
     RS_ALLOCATION_USAGE_IO_OUTPUT = 0x0040,
+    RS_ALLOCATION_USAGE_SHARED = 0x0080,
 
     RS_ALLOCATION_USAGE_ALL = 0x00FF
 };