The STL now defines `std::byte` so doing `using namespace std`
will conflict will custom definition of `byte`, which this
legacy code is full of.
It looks like NetRadiant went the route of making explicit
usage of `std::` prefixed types and did not renamed the
custom definition of byte, so doing the same reduces diff
noise between the two trees.
This also makes the code future proof if the STL decides
to define some other types with common name.
This patches replaces all usages of `map`, `pair` and
`vector` with `std::map`, `std::pair` and `std::vector`
and remove the `using namespace std` line in `stl_check.h`.
```
libs/mathlib.h:132:44: error: reference to ‘byte’ is ambiguous
132 | void NormalToLatLong( const vec3_t normal, byte bytes[2] );
| ^~~~
In file included from /usr/include/c++/11/bits/stl_algobase.h:61,
from /usr/include/c++/11/bits/char_traits.h:39,
from /usr/include/c++/11/ios:40,
from /usr/include/c++/11/ostream:38,
from /usr/include/c++/11/iostream:39,
from libs/missing.h:76,
from radiant/qe3.h:40,
from radiant/stdafx.h:39,
from radiant/bp_dlg.cpp:28:
/usr/include/c++/11/bits/cpp_type_traits.h:404:30: note: candidates are: ‘enum class std::byte’
404 | enum class byte : unsigned char;
| ^~~~
```
