patch 8.0.0902: cannot specify directory or environment for a job

Problem:    Cannot specify directory or environment for a job.
Solution:   Add the "cwd" and "env" arguments to job options. (Yasuhiro
            Matsumoto, closes #1160)
diff --git a/src/os_unix.c b/src/os_unix.c
index 141a3f0..c56de66 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -5320,6 +5320,22 @@
 # endif
 	    set_default_child_environment();
 
+	if (options->jo_env != NULL)
+	{
+	    dict_T	*dict = options->jo_env;
+	    hashitem_T	*hi;
+	    int		todo = (int)dict->dv_hashtab.ht_used;
+
+	    for (hi = dict->dv_hashtab.ht_array; todo > 0; ++hi)
+		if (!HASHITEM_EMPTY(hi))
+		{
+		    typval_T *item = &dict_lookup(hi)->di_tv;
+
+		    vim_setenv((char_u*)hi->hi_key, get_tv_string(item));
+		    --todo;
+		}
+	}
+
 	if (use_null_for_in || use_null_for_out || use_null_for_err)
 	    null_fd = open("/dev/null", O_RDWR | O_EXTRA, 0);
 
@@ -5387,6 +5403,9 @@
 	if (null_fd >= 0)
 	    close(null_fd);
 
+	if (options->jo_cwd != NULL && mch_chdir((char *)options->jo_cwd) != 0)
+	    _exit(EXEC_FAILED);
+
 	/* See above for type of argv. */
 	execvp(argv[0], argv);