Problem reported by Kevin Cernekee in:
http://lists.gnu.org/archive/html/bug-gnulib/2015-02/msg00092.html
* doc/glibc-functions/getdtablesize.texi (getdtablesize):
Mention that getdtablesize doesn't work on Android.
* lib/getdtablesize.c: Use getrlimit substitute only if
getdtablesize is declared. This should suffice for Cygwin
while not breaking Android.
* m4/dup2.m4 (gl_FUNC_DUP2):
* m4/fcntl.m4 (gl_FUNC_FCNTL):
Prefer sysconf (_SC_OPEN_MAX) to getdtablesize, as the former is
standardized but the latter is not, and sysconf works on Android.
* m4/getdtablesize.m4 (gl_FUNC_GETDTABLESIZE):
Also check that getdtablesize is declared.
This removes the need for a special case for Android.