Add syntax tests for declaration restrictions

test/language/statements/if/if-cls-else-cls.js

test/language/statements/if/if-cls-else-stmt.js

test/language/statements/if/if-cls-no-else.js

test/language/statements/if/if-const-else-const.js

test/language/statements/if/if-const-else-stmt.js

test/language/statements/if/if-const-no-else.js

test/language/statements/if/if-fun-else-fun-strict.js

test/language/statements/if/if-fun-else-stmt-strict.js

test/language/statements/if/if-fun-no-else-strict.js

test/language/statements/if/if-gen-else-gen.js

test/language/statements/if/if-gen-else-stmt.js

test/language/statements/if/if-gen-no-else.js

test/language/statements/if/if-let-else-let.js

test/language/statements/if/if-let-else-stmt.js

test/language/statements/if/if-let-no-else.js

test/language/statements/if/if-stmt-else-cls.js

test/language/statements/if/if-stmt-else-const.js

test/language/statements/if/if-stmt-else-fun-strict.js

test/language/statements/if/if-stmt-else-gen.js

test/language/statements/if/if-stmt-else-let.js