Update LIBLOUIS_CURRENT and LIBLOUIS_REVISION

Since we reverted the change that changed
liblouis.h.in (ac1f94f91413de5c5f6684f3d95aeca9351a17df) we no longer
need to increment LIBLOUIS_CURRENT. This only needs to be changed if
the interface has changes. However we now need to change
LIBLOUIS_REVISION as the source did indeed change.
diff --git a/configure.ac b/configure.ac
index a2d75bf..8660da6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -53,11 +53,11 @@
 ])
 
 # increment if the interface has additions, changes, removals.
-LIBLOUIS_CURRENT=17
+LIBLOUIS_CURRENT=16
 
 # increment any time the source changes; set to 0 if you increment
 # CURRENT
-LIBLOUIS_REVISION=0
+LIBLOUIS_REVISION=1
 
 # increment if any interfaces have been added; set to 0 if any
 # interfaces have been changed or removed. removal has precedence over