Currently CPP will silently convert line numbers from unsigned long to
unsigned int. It will also wrap-around line numbers higher than
ULONG_MAX. This patch adds a warning when any of these events occur.

Boostrapped and regression tested on x86_64-unknown-linux-gnu.

2008-02-27  Manuel Lopez-Ibanez  <manu@gcc.gnu.org>

  PR28079
libcpp/
  * directives.c (strtoul_for_line): Add a parameter 'wrapped'.
  (do_line): Update call to strtoul_for_line. Warn if wrapped or if truncated.
  (do_linemarker): Update call to strtoul_for_line.
testsuite/
  * gcc.dg/cpp/line6.c: New.