The boost::process example and my project also don't build on the latest version of boost 1.88.0

The example is taken from the previous version of boost 1.87.0 (https://www.boost.org/doc/libs/1_87_0/doc/html/process.html), because the latest version 1.88.0 does not contain documentation on Process.

```
#include

#include
#include

using namespace boost::process;

int main()
{
ipstream pipe_stream;
child c("gcc --version", std_out > pipe_stream);

std::string line;

while (pipe_stream && std::getline(pipe_stream, line) && !line.empty())
std::cerr << line << std::endl;

c.wait();
}
```

assembly line: `LANG=C g++ test.cpp`

compilation errors:

```
test.cpp:10:5: error: 'ipstream' was not declared in this scope
10 | ipstream pipe_stream;
| ^~~~~~~~
test.cpp:11:5: error: 'child' was not declared in this scope
11 | child c("gcc --version", std_out > pipe_stream);
| ^~~~~
test.cpp:15:12: error: 'pipe_stream' was not declared in this scope
15 | while (pipe_stream && std::getline(pipe_stream, line) && !line.empty())
| ^~~~~~~~~~~
test.cpp:18:5: error: 'c' was not declared in this scope
18 | c.wait();
| ^
```