optparse: avoid enum in optparse_get/set

Change prototype of optparse_get() and optparse_set() to avoid
passing an enum as the argument to va_start() in these variadic
functions. Use of enum causes newer compiler to issue warnings of
the form:

 passing an object that undergoes default argument promotion
 to 'va_start' has undefined behavior [-Werror,-Wvarargs]

Change the enum argument in these functions to an integer to suppress
the warning and avoid potential undefined behavior.

src/common/liboptparse/optparse.c

@@ -995,7 +995,7 @@ optparse_err_t optparse_add_doc (optparse_t *p, const char *doc, int group)
     return optparse_add_option (p, &o);
 }
 
-optparse_err_t optparse_set (optparse_t *p, optparse_item_t item, ...)
+optparse_err_t optparse_set (optparse_t *p, int item, ...)
 {
     optparse_err_t e = OPTPARSE_SUCCESS;
     va_list vargs;
@@ -1074,7 +1074,7 @@ static void * lookup_recursive (optparse_t *p, const char *key)
 }
 
 
-optparse_err_t optparse_get (optparse_t *p, optparse_item_t item, ...)
+optparse_err_t optparse_get (optparse_t *p, int item, ...)
 {
     optparse_err_t e = OPTPARSE_SUCCESS;
     va_list vargs;

src/common/liboptparse/optparse.h

@@ -243,9 +243,9 @@ optparse_err_t optparse_add_option_table (optparse_t *p,
  */
 optparse_err_t optparse_add_doc (optparse_t *p, const char *doc, int group);
 
-optparse_err_t optparse_set (optparse_t *p, optparse_item_t item, ...);
+optparse_err_t optparse_set (optparse_t *p, int item, ...);
 
-optparse_err_t optparse_get (optparse_t *p, optparse_item_t item, ...);
+optparse_err_t optparse_get (optparse_t *p, int item, ...);
 
 /*   Set and get arbitrary ancillary data associated with an optparse
  *    object. optparse_get_data () returns NULL if data not found.