Add negative tests of the parser.

test/static/bad/a-rule-is-expected.exp

+File "a-rule-is-expected.mly", line 5, characters 0-6:
+Error: syntax error after '%%' and before '%start'.
+A rule is expected at this point.

test/static/bad/a-rule-is-expected.mly

+(* The percentpercent sign is misplaced; it comes too early. *)
+
+%%
+
+%start<int> main
+%token A
+
+main:
+  A { 0 }

test/static/bad/actuals.exp

+File "actuals.mly", line 4, characters 12-13:
+Error: syntax error after ',' and before ')'.
+Ill-formed list of actual parameters.
+A comma-delimited list of actual parameters is expected at this point.
+Examples of well-formed actual parameters:
+  expr
+  expr+
+  option(expr)
+  separated_list(COMMA, expr)

test/static/bad/actuals.mly

+%%
+
+main:
+  foo(bar(A,))
+    {}

test/static/bad/after-a-semicolon.exp

+File "after-a-semicolon.mly", line 8, characters 0-6:
+Error: syntax error after ';' and before '%token'.
+After a semicolon, an expression is expected.
+(A rule cannot be terminated with a semicolon.)
+Examples of expressions:
+  term
+  t = term; { t }
+  LPAREN; ~ = term; RPAREN; <>

test/static/bad/after-a-semicolon.mly

+%token A B
+
+%%
+
+let main :=
+  A(B;
+
+%token FOO

test/static/bad/another-rule-is-expected.exp

+File "another-rule-is-expected.mly", line 9, characters 0-5:
+Error: syntax error after ';' and before '%type'.
+Another rule is expected at this point.

test/static/bad/another-rule-is-expected.mly

+%start<int> main
+%token A
+
+%%
+
+main:
+  A { 0 };
+
+%type<int> main

test/static/bad/choice-expression.exp

+File "choice-expression.mly", line 6, characters 0-6:
+Error: syntax error after ',' and before '%token'.
+An expression is expected at this point.
+Examples of expressions:
+  term
+  t = term; { t }
+  LPAREN; ~ = term; RPAREN; <>
+  factor | ~ = term; ~ = op; ~ = factor; <EBinOp>

test/static/bad/choice-expression.mly

+%%
+
+let main :=
+  A(B,
+
+%token A B

test/static/bad/closing-paren-expected.exp

+File "closing-paren-expected.mly", line 3, characters 6-7:
+Error: syntax error after 'X' and before ':'.
+Ill-formed rule.
+A closing parenthesis ')' is expected at this point.
+Examples of well-formed rules:
+  option(X): { None } | x = X { Some x }
+  pair(X, Y): x = X; y = Y { (x, y) }

test/static/bad/closing-paren-expected.mly

+%%
+
+main(X:
+  { () }

test/static/bad/colon.exp

+File "colon.mly", line 4, characters 2-3:
+Error: syntax error after ')' and before 'A'.
+Ill-formed rule.
+A colon ':' is expected at this point.
+Examples of well-formed rules:
+  option(X): { None } | x = X { Some x }

test/static/bad/colon.mly

+%%
+
+main(X)
+  A B X {}

test/static/bad/comma-delimited-list-expected.exp

+File "comma-delimited-list-expected.mly", line 3, characters 5-6:
+Error: syntax error after '(' and before ')'.
+Ill-formed rule.
+A comma-delimited list of formal parameters is expected at this point.
+Examples of well-formed rules:
+  option(X): { None } | x = X { Some x }
+  pair(X, Y): x = X; y = Y { (x, y) }

test/static/bad/comma-delimited-list-expected.mly

+%%
+
+main():
+  { () }

test/static/bad/commabar.exp

+File "commabar.mly", line 8, characters 0-6:
+Error: syntax error after '{}' and before '%token'.
+At this point, one of the following is expected:
+a comma ',' followed with an expression, or
+a bar '|' followed with an expression, or
+a closing parenthesis ')'.

test/static/bad/commabar.mly

+%token A B
+
+%%
+
+let main :=
+  A({}
+
+%token FOO

test/static/bad/either-a-semantic-action.exp

+File "either-a-semantic-action.mly", line 4, characters 12-13:
+Error: syntax error after 'foo' and before 'A'.
+Ill-formed rule.
+Either a semantic action '{' ... '}'
+or another production '|' ...
+is expected at this point.
+Examples of well-formed rules:
+  expr: MINUS e = expr %prec UMINUS { -e }

test/static/bad/either-a-semantic-action.mly

+%%
+
+main:
+  %prec foo A {}