package/php-amqp: fix build with php 7.3.0

package/php-amqp: fix build with php 7.3.0

This includes an upstream patch that fixes the following error:

```
/home/naourr/work/instance-1/output/build/php-amqp-1.9.3/amqp_channel.c: In function 'php_amqp_destroy_fci':
/home/naourr/work/instance-1/output/build/php-amqp-1.9.3/amqp_channel.c:104:37: error: lvalue required as decrement operand
             GC_REFCOUNT(fci->object)--;
                                     ^~
/home/naourr/work/instance-1/output/build/php-amqp-1.9.3/amqp_channel.c: In function 'php_amqp_duplicate_fci':
/home/naourr/work/instance-1/output/build/php-amqp-1.9.3/amqp_channel.c:115:40: error: lvalue required as increment operand
             GC_REFCOUNT(source->object)++;
                                        ^~
make[1]: *** [Makefile:206: amqp_channel.lo] Error 1
```

The patch was created from the commit at:

https://github.com/pdezwart/php-amqp/commit/1205d3287df0a9ec762a6594b4fa018ed9637d21

Upstream has not yet made an official release that includes it. Fixes:

http://autobuild.buildroot.net/results/222873a689f7b9da20acb3604b8364885e96b98d
http://autobuild.buildroot.net/results/90710cb2a4873f39aa75db79ff70aa9e4bdf83ae

Signed-off-by: Frank Hunleth <fhunleth@troodon-software.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>