Bump soname version for v0.5.

We've added tag copy/compare, server_info, decode_cb, set_dither.
Constification is backward-compatible.

configure.ac

@@ -33,9 +33,9 @@ dnl - interfaces added/removed/changed -> increment CURRENT, REVISION = 0
 dnl - interfaces added -> increment AGE
 dnl - interfaces removed -> AGE = 0
 
-OP_LT_CURRENT=2
+OP_LT_CURRENT=3
 OP_LT_REVISION=0
-OP_LT_AGE=2
+OP_LT_AGE=3
 
 AC_SUBST(OP_LT_CURRENT)
 AC_SUBST(OP_LT_REVISION)