Linux 3.10 compat: struct vmalloc_info moved

Linux kernel commmit torvalds/linux@db3808c1 moved the
vmalloc_info structure from a private to a public header.
Now that it's available for kernel modules use it.

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #257
Linux 3.10 compat: replace PDE()->data with PDE_DATA()

Linux kernel commit torvalds/linux@d9dda78b renamed PDE() to
PDE_DATA().  To handle this detect the prefered interface
and define a PDE_DATA() wrapper for consistency.

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #257
Linux 3.10 compat: add missing include of linux/slab.h

Linux kernel commit torvalds/linux@0d01ff2 changes some
includes we were depending on through linux/proc_fs.h.

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #257
Linux 3.10 compat: Do not rely on struct proc_dir_entry definition

Linux kernel commit torvalds/linux#59d8053f moved the definition of
struct proc_dir_entry from include/linux/proc_fs.h to the private
header fs/proc/internal.h. The SPL relied on that to map Solaris'
kstat to entries in /proc/spl/kstat.

Since the proc_dir_entry structure is now private the only safe
thing to do is wrap the opaque proc handle with our own structure.
This actually ends up simplify the code and is good because it
moves us away from depending on implementation details of /proc.

Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #257
Merge branch 'linux-3.10'

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #257