Fix lengths of 2**30 or more where long is 32 bits

#rest_size, #skip, #match?, #skip_until and #exist? passed the length to INT2FIX, which does not fit past FIXNUM_MAX. On x64-mswin64 the result printed as the right number but was not equal to it, and `rest_size + rest_size` came out negative.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: hsbt

ext/strscan/strscan.c

@@ -826,7 +826,7 @@ strscan_do_scan(VALUE self, VALUE pattern, int succptr, int getstr, int headonly
             return extract_beg_len(p, p->prev, length);
         }
         else {
-            return INT2FIX(length);
+            return LEN2NUM(length);
         }
     }
 }
@@ -2190,7 +2190,7 @@ strscan_rest_size(VALUE self)
         return INT2FIX(0);
     }
     i = S_RESTLEN(p);
-    return INT2FIX(i);
+    return LEN2NUM(i);
 }
 
 #define INSPECT_LENGTH 5