Change 'len' of linux_common_xfer_osdata to ULONGEST.

Change 'len' of linux_common_xfer_osdata to ULONGEST.

gdb:

2014-01-14  Yao Qi  <yao@codesourcery.com>

	* common/linux-osdata.c (linux_xfer_osdata_processes): Change
	type of 'len' to ULONGEST.
	(linux_xfer_osdata_processgroups): Likewise.
	(linux_xfer_osdata_threads): Likewise.
	(linux_xfer_osdata_fds): Likewise.
	(linux_xfer_osdata_isockets): Likewise.
	(linux_xfer_osdata_shm): Likewise.
	(linux_xfer_osdata_sem): Likewise.
	(linux_xfer_osdata_msg): Likewise.
	(linux_common_xfer_osdata): Likewise.
	(struct osdata_type) <getter>: Likewise.
	* common/linux-osdata.h (linux_common_xfer_osdata): Update
	the declaration.