Introduce parser-time optimization that moves function's argument values to registers.

For functions with the optimization applied:
 - vm puts arguments values immediately to registers without putting them to variables in lexical environment;
 - number of arguments is extracted from corresponding 'reg_var_decl' instruction's argument;
 - for functions that also don't have local variables, lexical environments are not created.

JerryScript-DCO-1.0-Signed-off-by: Ruben Ayrapetyan r.ayrapetyan@samsung.com

tests/unit/test-parser.cpp

@@ -121,7 +121,7 @@ main (int __attr_unused___ argc,
                 OPCODE_SCOPE_CODE_FLAGS_NOT_REF_ARGUMENTS_IDENTIFIER
                 | OPCODE_SCOPE_CODE_FLAGS_NOT_REF_EVAL_IDENTIFIER,
                 VM_IDX_EMPTY),
-    getop_reg_var_decl (1u, 0u),
+    getop_reg_var_decl (1u, 0u, 0u),
     getop_var_decl (0),                              // var a;
     getop_assignment (VM_REG_GENERAL_FIRST, 1, 1),   // $tmp0 = 1;
     getop_assignment (0, 6, VM_REG_GENERAL_FIRST),   // a = $tmp0;