Use c90 compatible comments

backend/v4l.c

@@ -290,7 +290,7 @@ init_options (V4L_Scanner * s)
   s->val[OPT_MODE].s = strdup (mode_list[0]);
   if (!s->val[OPT_MODE].s)
     return SANE_STATUS_NO_MEM;
-  s->opt[OPT_MODE].size = 1; // '\0'
+  s->opt[OPT_MODE].size = 1; /* '\0' */
   for (i = 0; mode_list[i] != 0; ++i)
     {
       int len = strlen(mode_list[i]) + 1;
@@ -312,7 +312,7 @@ init_options (V4L_Scanner * s)
     return SANE_STATUS_NO_MEM;
   if (s->channel[0] == 0 || s->channel[1] == 0)
     s->opt[OPT_CHANNEL].cap |= SANE_CAP_INACTIVE;
-  s->opt[OPT_CHANNEL].size = 1; // '\0'
+  s->opt[OPT_CHANNEL].size = 1; /* '\0' */
   for (i = 0; s->channel[i] != 0; ++i)
     {
       int len = strlen(s->channel[i]) + 1;