Merge from gnulib

Merge from gnulib

This gets Emacs working again with HP-UX Itanium cc.
It incorporates:
2017-03-19 stdalign: tweak version# and test for HP-UX IA64
2017-03-18 stdalign: restore previous behavior for HP-UX IA64
2017-03-17 stat-time, timespec: Support header files in C++ mode
2017-03-17 stdalign: Make it work with HP-UX cc
2017-03-17 flexmember: try to detect HP-UX 11.31 cc bug
2017-03-16 stdint: Fix test compilation failure with HP-UX 11 cc.
2017-03-14 gnulib-tool: don't produce tests with only snippets
2017-03-14 limits-h: Make it work with HP-UX cc.
* etc/PROBLEMS: Remove now-obsolete entry for HP-UX 11.31.
* lib/gnulib.mk.in, m4/gnulib-comp.m4: Regenerate.
* lib/limits.in.h, lib/stat-time.h, lib/stdalign.in.h:
* lib/stdint.in.h, lib/timespec.h, m4/flexmember.m4, m4/stdalign.m4:
Copy from gnulib.