fix read_cmdline API and a small buglet where "[comm]" may be too narrow

function                                             old     new   delta
func_args                                             25      26      +1
read_cmdline                                         119     114      -5
display_process_list                                1462    1447     -15
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/2 up/down: 1/-20)             Total: -19 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/include/libbb.h b/include/libbb.h
index 14a1667..fd61517 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -1359,9 +1359,9 @@
 //procps_status_t* alloc_procps_scan(void) FAST_FUNC;
 void free_procps_scan(procps_status_t* sp) FAST_FUNC;
 procps_status_t* procps_scan(procps_status_t* sp, int flags) FAST_FUNC;
-/* Format cmdline (up to col chars) into char buf[col+1] */
+/* Format cmdline (up to col chars) into char buf[size] */
 /* Puts [comm] if cmdline is empty (-> process is a kernel thread) */
-void read_cmdline(char *buf, int col, unsigned pid, const char *comm) FAST_FUNC;
+void read_cmdline(char *buf, int size, unsigned pid, const char *comm) FAST_FUNC;
 pid_t *find_pid_by_name(const char* procName) FAST_FUNC;
 pid_t *pidlist_reverse(pid_t *pidList) FAST_FUNC;