limit EINTR occurrences.

Also fix an analogous bug (not a regression) in the lzma module.

readline() takes a const char* and the other readline_until_enter_or_signal() implementation
already has const char*.

The PyObject_INIT() macros returns obj:

../cpython/Objects/methodobject.c:32:23: warning: expression result unused [-Wunused-value]
        PyObject_INIT(op, &PyCFunction_Type);
                      ^~
../cpython/Include/objimpl.h:139:69: note: expanded from macro 'PyObject_INIT'
    ( Py_TYPE(op) = (typeobj), _Py_NewReference((PyObject *)(op)), (op) )
                                                                    ^
1 warning generated.

(grafted from c80083ad142db2939507800c755082293a87f2de)

between tracemalloc_remove_trace() and tracemalloc_add_trace() to reduce the
risk of race condition.

tracemalloc_add_trace() cannot fail anymore in tracemalloc_realloc() when
tracemalloc_realloc() resizes a memory block.

PyGILState_Ensure()/PyGILState_Release() calls to the raw wrappers to simplify
the code.

Rename also tracemalloc_log_alloc/log_free() to
tracemalloc_add_trace/remove_trace().

can now avoid a second syscall if the ioctl() function can be used, or if the
non-blocking flag of the socket is unchanged.

Improve also wait() documentation: mention that the first parameter is a
sequence

Issue #19877: fix regression in test_pathlib when Windows has symlink support available (i.e. in administrator mode).
Patch by Vajrasky Kok.