hgdemandimport: disable on Python 3.5
The demand importer functionality isn't working at all on Python 3.5.
I'm not sure what's wrong.
Since it isn't working, let's disable it completely.
```
$ HGRCPATH= hyperfine -w 1 -r 50 -- "~/.pyenv/versions/3.5.9/bin/python ./hg version" \
"HGDEMANDIMPORT=disable ~/.pyenv/versions/3.5.9/bin/python ./hg version"
Benchmark #1: ~/.pyenv/versions/3.5.9/bin/python ./hg version
Time (mean ± σ): 163.7 ms ± 2.2 ms [User: 148.5 ms, System: 15.7 ms]
Range (min … max): 161.0 ms … 170.2 ms 50 runs
Benchmark #2: HGDEMANDIMPORT=disable ~/.pyenv/versions/3.5.9/bin/python ./hg version
Time (mean ± σ): 164.3 ms ± 1.4 ms [User: 148.2 ms, System: 16.6 ms]
Range (min … max): 161.4 ms … 169.8 ms 50 runs
```
Differential Revision: https://phab.mercurial-scm.org/D7953
/*
* A command server client that uses Unix domain socket
*
* Copyright (c) 2011 Yuya Nishihara <yuya@tcha.org>
*
* This software may be used and distributed according to the terms of the
* GNU General Public License version 2 or any later version.
*/
#ifndef HGCLIENT_H_
#define HGCLIENT_H_
#include <sys/types.h>
struct hgclient_tag_;
typedef struct hgclient_tag_ hgclient_t;
hgclient_t *hgc_open(const char *sockname);
void hgc_close(hgclient_t *hgc);
pid_t hgc_peerpgid(const hgclient_t *hgc);
pid_t hgc_peerpid(const hgclient_t *hgc);
const char **hgc_validate(hgclient_t *hgc, const char *const args[],
size_t argsize);
int hgc_runcommand(hgclient_t *hgc, const char *const args[], size_t argsize);
void hgc_attachio(hgclient_t *hgc);
void hgc_setenv(hgclient_t *hgc, const char *const envp[]);
#endif /* HGCLIENT_H_ */