Includes C++26 related infrastructure macros.
Fixes compile errors when compiling under C++26.
Initially supported C++26 features:
- [[indeterminate]]
- new 2022 ISO prefixes in ratio.h
- atomic fetch_max() and fetch_min()
- is_virtual_base_of
- is_trivially_relocatable and trivially_relocate
- saturation arithmetic: add_sat, sub_sat, mul_sat, div_sat, saturate_cast
For non-GCC-compilers, the template keyword is being used in
parameter_pack.h for referring to a template template member.
However, clang 19 and 20 don't accept this.
It should be verified which compiler really needs the template
keyword here at all. If not, the if-branch can be removed.
Removed redundant ETL_USING_WIDE_CHARACTERS
Added using_libc_wchar_h to ETL traits
#1127 type_traits.h and C++03
Changed many instances of mem_copy to mem_move
