error: Make error_setg() a function

Saves a tiny amount of code at every call site.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>

include/qapi/error.h

@@ -51,8 +51,8 @@ void error_set_win32(Error **errp, int win32_err, ErrorClass err_class,
 /**
  * Same as error_set(), but sets a generic error
  */
-#define error_setg(errp, fmt, ...) \
-    error_set(errp, ERROR_CLASS_GENERIC_ERROR, fmt, ## __VA_ARGS__)
+void error_setg(Error **errp, const char *fmt, ...)
+    GCC_FMT_ATTR(2, 3);
 #define error_setg_errno(errp, os_error, fmt, ...) \
     error_set_errno(errp, os_error, ERROR_CLASS_GENERIC_ERROR, \
                     fmt, ## __VA_ARGS__)

util/error.c

@@ -56,6 +56,15 @@ void error_set(Error **errp, ErrorClass err_class, const char *fmt, ...)
     va_end(ap);
 }
 
+void error_setg(Error **errp, const char *fmt, ...)
+{
+    va_list ap;
+
+    va_start(ap, fmt);
+    error_setv(errp, ERROR_CLASS_GENERIC_ERROR, fmt, ap);
+    va_end(ap);
+}
+
 void error_set_errno(Error **errp, int os_errno, ErrorClass err_class,
                      const char *fmt, ...)
 {