soup-headers: Update UTF-8 header param handling for RFC 5987
soup-headers: Update UTF-8 header param handling for RFC 5987

Update the handling of UTF-8 header parameters for the
changes/clarifications to RFC 2231 published in RFC 5987:

    * Decode iso-8859-1 params in addition to UTF-8 ones
    * An encoded UTF-8 param should override an unencoded param
      of the same name, regardless of which order they appear in

fanc999/libsoup,fanc999/libsoup,ahmedammar/platform_external_gst_libsoup,Distrotech/libsoup,jwendell/libsoup,Distrotech/libsoup,fanc999/libsoup,Distrotech/libsoup,ahmedammar/platform_external_gst_libsoup,Distrotech/libsoup,jwendell/libsoup,Distrotech/libsoup,jwendell/libsoup,ahmedammar/platform_external_gst_libsoup,fanc999/libsoup,jwendell/libsoup,fanc999/libsoup,jwendell/libsoup