System-dependent integer overflow fixes.

System-dependent integer overflow fixes.

* process.c (Fset_process_window_size): Signal an error if
the window size is outside the range supported by the lower level.
* sysdep.c (set_window_size): Return negative on error,
nonnegative on success, rather than -1, 0, 1 on not in system,
failure, success.  This is simpler.  Caller changed.
(serial_configure): Remove unnecessary initialization of local.
(procfs_get_total_memory) [GNU_LINUX]: Don't assume system memory
size fits in unsigned long; this isn't true on some 32-bit hosts.
Avoid buffer overrun if some future version of /proc/meminfo has a
variable name longer than 20 bytes.
(system_process_attributes) [__FreeBSD__]:
Don't assume hw.availpages fits in 'int'.