hoa: catch redefinition of states

* src/hoaparse/hoaparse.yy: Here.
* src/tgbatest/hoaparse.test: More test.

src/tgbatest/hoaparse.test

@@ -85,6 +85,24 @@ input:10.5: state number is larger than state count...
 input:2.1-9: ... declared here.
 EOF
 
+cat >input <<EOF
+HOA: v1
+States: 1
+Start: 0
+AP: 1 "a"
+Acceptance: 1 Inf(0)
+--BODY--
+State: 0 {0}
+[0] 0
+State: 0 {0}
+[t] 0
+--END--
+EOF
+
+expecterr input <<EOF
+input:9.1-8: redeclaration of state 0
+EOF
+
 cat >input <<EOF
 HOA: v1
 States: 0