Bump SONAME to reflect the ABI break.

Fixes #243.

Change-Id: Id553565b88df9ce42643053c2163fa457b69a649
Reviewed-on: https://code-review.googlesource.com/c/re2/+/52736
Reviewed-by: Paul Wankadia <junyer@google.com>
diff --git a/Makefile b/Makefile
index 5cc539d..d0107ed 100644
--- a/Makefile
+++ b/Makefile
@@ -44,7 +44,7 @@
 
 # ABI version
 # http://tldp.org/HOWTO/Program-Library-HOWTO/shared-libraries.html
-SONAME=0
+SONAME=1
 
 # To rebuild the Tables generated by Perl and Python scripts (requires Internet
 # access for Unicode data), uncomment the following line: