glsl: Add method to determine whether an expression contains the sequence operator

This will be used in the next patch to enforce some language sematics.

v2: Fix inverted logic in
ast_function_expression::has_sequence_subexpression.  The method
originally had a different name and a different meaning.  I fixed the
logic in ast_to_hir.cpp, but I only changed the names in
ast_function.cpp.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Marta Lofstedt <marta.lofstedt@intel.com> [v1]
Reviewed-by: Matt Turner <mattst88@gmail.com>
Cc: "10.6 11.0" <mesa-stable@lists.freedesktop.org>

src/glsl/ast_function.cpp

@@ -1999,6 +1999,17 @@ ast_function_expression::hir(exec_list *instructions,
    unreachable("not reached");
 }
 
+bool
+ast_function_expression::has_sequence_subexpression() const
+{
+   foreach_list_typed(const ast_node, ast, link, &this->expressions) {
+      if (ast->has_sequence_subexpression())
+         return true;
+   }
+
+   return false;
+}
+
 ir_rvalue *
 ast_aggregate_initializer::hir(exec_list *instructions,
                                struct _mesa_glsl_parse_state *state)