efl/ui_format: Use STRING type for format strings that contain %%

Summary: This fixes progressbar format strings that contain the pattern %%, thus making it a string and not a format.

Test Plan: elementary_test progressbar shows %% on the first vertical progressbar before this patch.  afterwords it shows % correctly.

Reviewers: zmike

Reviewed By: zmike

Subscribers: cedric, #reviewers, #committers, zmike

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D6790

src/lib/efl/interfaces/efl_ui_format.c

@@ -38,6 +38,7 @@ _format_string_check(const char *fmt)
         if (itr[1] == '%')
           {
              itr++;
+             ret_type = FORMAT_TYPE_STRING;
              continue;
           }