all: add and utilize nm_utils_is_separator()

It is meant to be rather similar in nature to isblank() or
g_ascii_isspace().

Sadly, isblank() is locale dependent while g_ascii_isspace() also considers
vertical whitespace as a space. That's no good for configuration files that
are strucutured into lines, which happens to be a pretty common case.

clients/cli/connections.c

@@ -5884,7 +5884,7 @@ _split_cmd (const char *cmd, char **out_arg0, const char **out_argr)
 
 	if (!cmd)
 		return;
-	while (NM_IN_SET (cmd[0], ' ', '\t'))
+	while (nm_utils_is_separator (cmd[0]))
 		cmd++;
 	if (!cmd[0])
 		return;
@@ -5893,7 +5893,7 @@ _split_cmd (const char *cmd, char **out_arg0, const char **out_argr)
 	arg0 = g_strndup (cmd, l);
 	cmd += l;
 	if (cmd[0]) {
-		while (NM_IN_SET (cmd[0], ' ', '\t'))
+		while (nm_utils_is_separator (cmd[0]))
 			cmd++;
 		if (cmd[0])
 			argr = cmd;

clients/common/nm-meta-setting-desc.c

@@ -2157,7 +2157,7 @@ _get_fcn_802_1x_phase2_private_key (ARGS_GET_FCN)
 		password = path + strcspn (path, " \t"); \
 		if (password[0] != '\0') { \
 			password[0] = '\0'; \
-			while (NM_IN_SET (password[0], ' ', '\t')) \
+			while (nm_utils_is_separator (password[0])) \
 				password++; \
 		} else \
 			password = password_free = g_strdup (pwd_func (NM_SETTING_802_1X (setting))); \

shared/nm-utils/nm-shared-utils.h

@@ -191,6 +191,12 @@ void nm_utils_strbuf_append_str (char **buf, gsize *len, const char *str);
 
 const char *nm_strquote (char *buf, gsize buf_len, const char *str);
 
+static inline gboolean
+nm_utils_is_separator (const char c)
+{
+	return NM_IN_SET (c, ' ', '\t');
+}
+
 /*****************************************************************************/
 
 const char **nm_utils_strsplit_set (const char *str, const char *delimiters);

src/settings/plugins/ifcfg-rh/nms-ifcfg-rh-reader.c

@@ -502,7 +502,7 @@ parse_route_line_is_comment (const char *line)
 	 *
 	 * initscripts compares: "$line" =~ '^[[:space:]]*(\#.*)?$'
 	 */
-	while (NM_IN_SET (line[0], ' ', '\t'))
+	while (nm_utils_is_separator (line[0]))
 		line++;
 	if (NM_IN_SET (line[0], '\0', '#'))
 		return TRUE;