avoid using strok - eliminates use of hidden global variable

function                                             old     new   delta
udhcp_str2optset                                     616     650     +34
setpriv_main                                         950     975     +25
switch_root_main                                     688     706     +18
parse                                                958     970     +12
getopt_main                                          622     628      +6
parse_resolvconf                                     302     306      +4
mpstat_main                                         1139    1142      +3
static.p                                               4       -      -4
cdcmd                                                717     702     -15
strtok                                               148       -    -148
------------------------------------------------------------------------------
(add/remove: 0/3 grow/shrink: 7/1 up/down: 102/-167)          Total: -65 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/util-linux/switch_root.c b/util-linux/switch_root.c
index c65096c..f2674b5 100644
--- a/util-linux/switch_root.c
+++ b/util-linux/switch_root.c
@@ -164,7 +164,7 @@
 {
 	char *cap;
 
-	cap = strtok(string, ",");
+	cap = strtok_r(string, ",", &string);
 	while (cap) {
 		unsigned cap_idx;
 
@@ -174,7 +174,7 @@
 		drop_bounding_set(cap_idx);
 		drop_capset(cap_idx);
 		bb_error_msg("dropped capability: %s", cap);
-		cap = strtok(NULL, ",");
+		cap = strtok_r(NULL, ",", &string);
 	}
 }
 #endif