asn1: Allow comments and leading ws in opt files

lib/asn1/asn1_compile.1

@@ -330,6 +330,11 @@ to form the names of the files generated.
 .It Fl Fl option-file=FILE
 Take additional command-line options from
 .Ar FILE .
+The options file must have one command-line option per-line, but
+leading whitespace is ignored, and lines that start with a hash
+symbol 
+.Sq ( # )
+are comments and are ignored.
 .It Fl Fl original-order
 Attempt to preserve the original order of type definition in the
 ASN.1 module.

lib/asn1/main.c

@@ -409,8 +409,16 @@ main(int argc, char **argv)
         sz = 2;
 
 	while (fgets(buf, sizeof(buf), opt) != NULL) {
+            size_t buflen, ws;
+
 	    buf[strcspn(buf, "\n\r")] = '\0';
 
+            buflen = strlen(buf);
+            if ((ws = strspn(buf, " \t")))
+                memmove(buf, buf + ws, buflen -= ws);
+            if (buf[0] == '\0' || buf[0] == '#')
+                continue;
+
             if (len + 1 >= sz) {
                 arg = realloc(arg, (sz + (sz>>1) + 2) * sizeof(arg[0]));
                 if (arg == NULL) {