* Fix -Wsign-conversion in bigint::subtract_aligned.

n is assigned a size_t, and only used for comparisons with j.

j is assigned 0, compared to n (size_t), and passed to basic_memory_buffer::operator[] (size_t).

* Fix -Wsign-conversion in bigint::assign.

num_bigits is initialised to 0, is only ever incremented, and is passed to basic_memory_buffer::operator[] (size_t) and basic_memory_buffer::resize (size_t).

Previously format.h defined FMT_CLANG_VERSION after including core.h, however core.h tests FMT_CLANG_VERSION when it defines FMT_API.

When building with -Werror,-Wmissing-noreturn clang identifies that assert_fail could be declared with the 'noreturn' attribute.

The current `FMT_FORMAT_AS` macro will make `formatter<Char *>::format`
have the first argument type `const Char *&` which is incorrect an
should be `Char *const &`.  This pull request fixes that by changing the
first argument type in the macro definition body from `const Type &` to
`Type const &`.

* improved use of find

*begin is supposed to be different from '{' when this find is used, so we can avoid checking it.

* add const begin and end overload to buffer

since there is a const overload for data I think there should also be one for begin and end

Make FMT_API symbols use the default visibility on non-Windows
platforms. Otherwise, one cannot use the generated fmt library when
compiling globally with -fvisibility=hidden.

Fixes compile errors like:

```
../3rdParty/fmt/include/fmt/core.h:757: error: undefined reference to 'fmt::v6::internal::assert_fail(char const*, int, char const*)'
```

Note that the symbol exists, but is local:

```
$ nm -C libfmtd.so.6.1.3  | grep assert_fail
                 U __assert_fail
0000000000233ffa t fmt::v6::internal::assert_fail(char const*, int, char const*)
```

With this patch, the compile error is gone and the symbol is properly
exported:

```
$ nm -a bin/libfmtd.so -C | grep assert_fail
                 U __assert_fail
00000000002366ba T fmt::v6::internal::assert_fail(char const*, int, char const*)
```

Change-Id: I96054e622d9a2ae81907e1b01a1033e629767a91

Simplify getting library name.

Add FMT_DEBUG_SUFFIX variable.

* Fix formatting chrono durations to wide strings

* Make format buffers const correct

* Add FormatWide chrono test case

* Fix incorrect wide encoding of 'µs'
I think might be a source file encoding issue, so I used \u00B5 instead.

* Update FormatWide test to use proper encoding of µs

* Revert changes to format_localized's parameters

* Use different overload of `std::time_put<T>::put` to avoid needing a format string

* Use utf8_to_utf16 instead of having redundant overloads of get_units

* Revert some minor changes

* Remove FMT_CONSTEXPR from expression

This should hopefully fix compilation on VS <2019

* Make suggested changes from code review

* Run clang-format on chrono.h

* Make sure unit isn't null before constructing a string_view from it

If `FMT_STATIC_THOUSANDS_SEPARATOR` defined, then locale is not included or defined, so this call will be unresolved.  I think this is the correct fix based on the code in `format-inl.h` and `format.h`