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
