Created cprover_loop_contract

1. Created cprover_loop_contract that has cprover_contract_assigns_opt and loop_invariant_opt.

This adds support for parsing assigns clauses for loops.

Author: Aalok Thakkar

src/ansi-c/parser.y

@@ -2418,7 +2418,7 @@ declaration_or_expression_statement:
 
 iteration_statement:
         TOK_WHILE '(' comma_expression_opt ')'
-          loop_invariant_opt statement
+          cprover_loop_contract statement
         {
           $$=$1;
           statement($$, ID_while);
@@ -2428,7 +2428,7 @@ iteration_statement:
             parser_stack($$).add(ID_C_spec_loop_invariant).swap(parser_stack($5));
         }
         | TOK_DO statement TOK_WHILE '(' comma_expression ')'
-          loop_invariant_opt ';'
+          cprover_loop_contract ';'
         {
           $$=$1;
           statement($$, ID_dowhile);
@@ -2449,7 +2449,7 @@ iteration_statement:
           '(' declaration_or_expression_statement
               comma_expression_opt ';'
               comma_expression_opt ')'
-              loop_invariant_opt
+              cprover_loop_contract 
           statement
         {
           $$=$1;
@@ -3271,6 +3271,12 @@ cprover_function_contract_sequence_opt:
         | cprover_function_contract_sequence
         ;
 
+cprover_loop_contract:
+          cprover_contract_assigns_opt
+          loop_invariant_opt
+        | loop_invariant_opt
+        ;
+
 postfixing_abstract_declarator:
           parameter_postfixing_abstract_declarator
         /* The following two rules implement K&R headers! */