fmtlib: updated to 6.0.0

6.0.0:
Switched to the MIT license with an optional exception that allows distributing binary code without attribution.
Floating-point formatting is now locale-independent by default.
Added an experimental Grisu floating-point formatting algorithm implementation (disabled by default). To enable it compile with the FMT_USE_GRISU macro defined to 1.
Separated formatting and parsing contexts for consistency with C++20 std::format, removing the undocumented basic_format_context::parse_context() function.
Added oss-fuzz support.
formatter specializations now always take precedence over operator<<.
Introduced the experimental fmt::compile function that does format string compilation.
Added the % format specifier that formats floating-point values as percentages.
Implemented precision for floating-point durations.
Implemented chrono format specifiers %Q and %q that give the value and the unit respectively .
Fixed handling of dynamic width in chrono formatter.
Removed deprecated fmt/time.h. Use fmt/chrono.h instead.
Added fmt::format and fmt::vformat overloads that take text_style.
Removed the deprecated color API (print_colored). Use the new API, namely print overloads that take text_style instead.
Made std::unique_ptr and std::shared_ptr formattable as pointers via fmt::ptr.
Made print and vprint report I/O errors.
Marked deprecated APIs with the [[deprecated]] attribute and removed internal uses of deprecated APIs.
Modernized the codebase using more C++11 features and removing workarounds. Most importantly, buffer_context is now an alias template, so use buffer_context<T> instead of buffer_context<T>::type. These features require GCC 4.8 or later.
formatter specializations now always take precedence over implicit conversions to int and the undocumented convert_to_int trait is now deprecated.
Moved the undocumented basic_writer, writer, and wwriter types to the internal namespace.
Removed deprecated basic_format_context::begin(). Use out() instead.
Disallowed passing the result of join as an lvalue to prevent misuse.
Refactored the undocumented structs that represent parsed format specifiers to simplify the API and allow multibyte fill.
Moved SFINAE to template parameters to reduce symbol sizes.
Switched to fputws for writing wide strings so that it's no longer required to call _setmode on Windows.

(adam)