It turns out that on 32-bit Linux, ss_file_size() returns the wrong answer for
files bigger than 2 GB (4GB?). The Linux stat() system call returns an error
(which is ignored) and bogus file size data (returned to the caller).

On 64-bit Linux (compiled with -m64), stat() appears to return correct data.

Related functions ss_disk_size() and ss_disk_free() return correct answers on
both 32-bit and 64-bit Linux (biggest disk I tried was 5.5 TB).

I now fixed this problem by using the stat64() system call for "#ifdef OS_LINUX".

I also changed ss_file_size(), ss_disk_size() and ss_disk_free() to return -1 if
the system call returns an error. I also added a test program
utils/test_ss_file_size.c.

svn revision 4397.
K.O.