Linux: compiler errors for ToLongEx(), ToDoubleEx() implementation

[GWRon]

[ 42%] Compiling:blitz_string_ex.cpp
/build/temp/BlitzMax/mod/brl.mod/blitz.mod/blitz_string_ex.cpp: In function 'int bbStringToDoubleEx(BBString*, double*, int, int, BBULONG, BBString*)':
/build/temp/BlitzMax/mod/brl.mod/blitz.mod/blitz_string_ex.cpp:48:14: error: expected unqualified-id before '[' token
         auto [ptr, ec] = fast_float::from_chars_advanced(p, e, result, options);
              ^
/build/temp/BlitzMax/mod/brl.mod/blitz.mod/blitz_string_ex.cpp:49:13: error: 'ptr' was not declared in this scope
         if (ptr != nullptr) {
             ^

Further detailes in the log of the failed github-action for the weekly build:
https://github.com/bmx-ng/bmx-ng/actions/runs/12450294810/job/34756965551

[GWRon]

According to
https://gcc.gnu.org/projects/cxx-status.html

Structured bindings are available from GCC 7 on:
Structured bindings [P0217R3]
(https://wg21.link/p0217) 7 __cpp_structured_bindings >= 201606

The build environment of Ubuntu 16 provides GCC 5.4.0

Structured bindings could possibly be avoided there by doing it this way:
current:

    if ( sepChar != 0 && sepChar != '.' ) {
        fast_float::parse_options_t<char16_t> options{static_cast<fast_float::chars_format>(format), sepChar};
        auto [ptr, ec] = fast_float::from_chars_advanced(p, e, result, options);
        if (ptr != nullptr) {
            *val = result;
            return ptr - start;
        }
    }

new:

    if ( sepChar != 0 && sepChar != '.' ) {
        fast_float::parse_options_t<char16_t> options{static_cast<fast_float::chars_format>(format), sepChar};
        auto result_pair = fast_float::from_chars_advanced(p, e, result, options);
        auto ptr = result_pair.first;
        auto ec = result_pair.second;
        if (ptr != nullptr) {
            *val = result;
            return ptr - start;
        }
    }