Update version to 2.9.0

Bump SOVERSION for parity with 2.7.2 and 2.7.3.
diff --git a/library/Makefile b/library/Makefile
index 0333815..97f796f 100644
--- a/library/Makefile
+++ b/library/Makefile
@@ -33,7 +33,7 @@
 
 SOEXT_TLS=so.10
 SOEXT_X509=so.0
-SOEXT_CRYPTO=so.1
+SOEXT_CRYPTO=so.2
 
 # Set DLEXT=dylib to compile as a shared library for Mac OS X
 DLEXT ?= so