change options argument type to unsigned int

[stevengj]

This PR changes argument-type declarations of the form utf8proc_option_t options to unsigned int options. The former is technically incorrect (though it worked in practice) because this argument is not in general an enumerated value, but is rather a bitwise-OR of enumerated values.

(This change doesn't break the ABI, because the byte representation of enum is the same as that of unsigned int on all widely available systems, I think, even though strictly speaking this is not required by the C standard?)

I noticed this because gcc was emitting warnings like:

test/custom.c:20:99: warning: implicit conversion from
      'int' to enumeration type 'utf8proc_option_t' is invalid in C++
      [-Wimplicit-int-enum-cast]
   20 |     utf8proc_map_custom(input, 0, &output, UTF8PROC_CASEFOLD | UTF8PROC_COMPOSE | UTF8PROC_COMPAT | UTF8PROC_NULLTERM,

Originally, these option constants were #define preprocessor constants, but they were changed to an enum by #29.