Check if VCF POS column could be fully parsed

and throw an error if not.

The position too large error report is also fixed so that it
reports the incorrect value instead of an empty string.

Resolves #1570

Co-authored-by: Rob Davies <rmd+git@sanger.ac.uk>

vcf.c

@@ -3232,9 +3232,13 @@ int vcf_parse(kstring_t *s, const bcf_hdr_t *h, bcf1_t *v)
             v->rid = kh_val(d, k).id;
         } else if (i == 1) { // POS
             overflow = 0;
+            char *tmp = p;
             v->pos = hts_str2uint(p, &p, 63, &overflow);
             if (overflow) {
-                hts_log_error("Position value '%s' is too large", p);
+                hts_log_error("Position value '%s' is too large", tmp);
+                goto err;
+            } else if ( *p ) {
+                hts_log_error("Could not parse the position '%s'", tmp);
                 goto err;
             } else {
                 v->pos -= 1;