variables: add branch to TWRP version number

Since the 9.0 and 10.0 TWRP branches have diverged due to adding
dynamic partition support, this will make it easier to understand
which branch of TWRP is being used for the build.

Change-Id: I2712c9498c9230e9a6d2eac718bda9e82a6d14f7
diff --git a/variables.h b/variables.h
index 95946b7..e96f7be 100755
--- a/variables.h
+++ b/variables.h
@@ -17,7 +17,7 @@
 #ifndef _VARIABLES_HEADER_
 #define _VARIABLES_HEADER_
 
-#define TW_MAIN_VERSION_STR       "3.4.0"
+#define TW_MAIN_VERSION_STR       "3.4.0_10"
 #define TW_VERSION_STR TW_MAIN_VERSION_STR TW_DEVICE_VERSION
 
 #define TW_USE_COMPRESSION_VAR      "tw_use_compression"