[C-libcurl] Assign the data type to the function parameter when it is "Free Form Object" in OpenAPI description(swagger.json)

Created by: ityuhui

When the type of a prameter is a "free form object" in OpenAPI description file (e.g. k8s swagger.json file),

e.g. The type of the parameter "body" is "object"

"parameters": [
          {
...
            "name": "body",
...
            "schema": {
...
              "type": "object"
            }
          },

The generated C-libcurl code cannot assign a right data type to the function parameter e.g. the paramter "body" cannot get data type

v1_mutating_webhook_configuration_t*
AdmissionregistrationV1API_patchAdmissionregistrationV1MutatingWebhookConfiguration(apiClient_t *apiClient ,char * name , body ,...);

This will cause building error.

The root cause is : the template code has not the handler for "free form object" for the function parameter, so I add below code:

{{#isFreeFormObject}}{{dataType}}_t *{{/isFreeFormObject}}

to the function definition and declaration template code.

PR checklist

• Read the contribution guidelines.
• If contributing template-only or documentation-only changes which will change sample output, build the project before.
• Run the shell script(s) under ./bin/ (or Windows batch scripts under.\bin\windows) to update Petstore samples related to your fix. This is important, as CI jobs will verify all generator outputs of your HEAD commit, and these must match the expectations made by your contribution. You only need to run ./bin/{LANG}-petstore.sh, ./bin/openapi3/{LANG}-petstore.sh if updating the code or mustache templates for a language ({LANG}) (e.g. php, ruby, python, etc).
• File the PR against the master: master, 4.3.x, 5.0.x. Default: master.
• Copy the technical committee to review the pull request if your PR is targeting a particular programming language.

@wing328 @zhemant