libxshmfence: Changes to 'master'

[Keith Packard]

 configure.ac          |    6 ++++++
 src/xshmfence_alloc.c |   50 ++++++++++++++++++++++++++++++++++++++++++--------
 2 files changed, 48 insertions(+), 8 deletions(-)

New commits:
commit b63ea144a0439c54a3a147274afeeb115caced5a
Author: Keith Packard <keithp at keithp.com>
Date:   Thu Oct 9 14:01:21 2014 +0200

    Use linux 3.17 memfd_create syscall when available
    
    Linux 3.17 introduces a new anonymous memory allocation that returns a
    file descriptor which we can pass around. Use this in preference to
    creating a file in the filesystem where available.
    
    Signed-off-by: Keith Packard <keithp at keithp.com>