php: fix build on C libraries that don't provide AI_IDN

The PHP sockets module now provides access to AI_IDN functionality (by
simply declaring a bunch of constants available from PHP code). AI_IDN
(internationalized domain names) is not supported in uClibc or musl,
which breaks the build.

This commit adds a patch to PHP which makes the use of AI_IDN
conditional, in a way that is identical to what is already done for
AI_ALL. The patch has been submitted upstream.

Fixes:

  http://autobuild.buildroot.net/results/ef040cc45bb2789ead82a8c445db3376e36b5ac7/



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>