Test for correct setting of errno.

Test for correct setting of errno.

This patch adds tests for POSIX and Linux specific syscalls
that implemented with syscall templates machinery. The reason
of tests is to receive the expected error code and test if
it's handled properly by glibc.

2017-03-08  Yury Norov <ynorov@caviumnetworks.com>
	    Zack Weinberg  <zackw@panix.com>

	* posix/test-errno.c: New file.
	* posix/Makefile (tests): Add test-errno.
	* sysdeps/unix/sysv/linux/test-errno.c: New file.
	* sysdeps/unix/sysv/linux/Makefile (tests): Add test-errno.