clang-13 needed an operator==(const exact_type<T>&) defined to avoid an
ambiguity. Now that C++20 mode is enabled, switch to a
compiler-generated operator== instead of manually defining the
equivalent function.
clang-13 in C++20 mode fails:
```
similar/main/newmenu.cpp:202:18: error: ISO C++20 considers use of overloaded operator '==' (with operand types 'exact_type<const dcx::grs_font>' and 'exact_
type<const dcx::grs_font>') to be ambiguous despite there being a unique best viable function [-Werror,-Wambiguous-reversed-operator]
return &cv_font == &game_font ? "\202" : "\207"; // 135
~~~~~~~~ ^ ~~~~~~~~~~
common/include/pack.h:31:17: note: ambiguity is between a regular call to this operator and a call with the argument order reversed
constexpr bool operator==(const T *rhs) const { return p == rhs; }
^
```
Add an operator== that exactly matches the input types so that clang
does not attempt a conversion.
Delete stub "compiler-type_traits.h" header. Redirect all uses to the
standard <type_traits> header.
git grep -wlz 'compiler-type_traits.h' -- '*.cpp' '*.h' | xargs -0 perl -p -i <<EOF
BEGIN {
$i = 0;
}
if (($i == 1 && $_ eq "\n") || ($i < 2 && /^#include "/)) {
# First blank line or first user-include after a system-include.
# Print, then never again for this file.
print "#include <type_traits>\n";
$i = 2;
} elsif ($i == 0) {
$i = 1 if (/^#include </);
} elsif ($_ eq "#include \"compiler-type_traits.h\"\n") {
# Remove this line if found.
$_ = '';
}
# Reset state machine when moving to next file.
$i = 0 if eof;
EOF
All supported compilers have an acceptable <type_traits>. Commit
4cb3d46148 ("Move <type_traits> test to Cxx11RequiredFeature") made
<type_traits> support mandatory in August and no one has objected.
Remove the indirection and use namespace std directly for type_traits
members.
Various functions use the non-macro form, so support for =delete is
already mandatory. Remove the remnants of support for compilers which
lack =delete and replace it with a hard stop when the compiler rejects
declaring explicitly deleted functions.
