tar: remove lint discovered by Sun C compiler
* src/common.h (WARN_ALL): Don't mask with 0xffffffff; on a 32-bit
host, 0xffffffff is of type 'unsigned int', which makes WARN_ALL
an unsigned int value that is too large to fit into an int, and
the C standard says that this has undefined behavior. The mask is
not needed, so omit it.