Added Dockerfile that runs test for PHP 7.3

docker/7.3/Dockerfile

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+FROM php:7.3-stretch
+
+ENV CFLAGS="-fstack-protector-strong -fpic -fpie -O2"
+ENV CPPFLAGS="$PHP_CFLAGS"
+ENV LDFLAGS="-Wl,-O1 -Wl,--hash-style=both -pie"
+
+ENV PECL_MEMCACHE_URL_GIT="https://github.com/websupport-sk/pecl-memcache.git"
+
+RUN apt-get update && apt-get install -y \ 
+	git \
+	zlib1g-dev \
+	memcached ; 
+
+RUN mkdir -p /var/run/memcached
+RUN chown memcache:memcache /var/run/memcached
+
+COPY host.conf /etc/host.conf
+
+RUN set -eux;\
+	cd /usr/src; \
+	\
+	git clone "$PECL_MEMCACHE_URL_GIT"; \
+	\
+	cd pecl-memcache; \
+	phpize ; \
+	./configure ; \
+	make -j2; 
+
+RUN echo "" 
+
+COPY start.sh /
+CMD ["/start.sh"]

docker/7.3/host.conf

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+order hosts,bind
+multi off

docker/7.3/start.sh

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+#!/bin/bash
+
+# Spawn memcached for tests
+/usr/bin/memcached -m 64 -u memcache -l 127.0.0.1 -s /var/run/memcached/memcached.sock -d
+/usr/bin/memcached -m 64 -u memcache -U 11211 -l 127.0.0.1 -p 11211 -d
+/usr/bin/memcached -m 64 -u memcache -U 11212 -l 127.0.0.1 -p 11212 -d
+
+# Let's start tests
+cd /usr/src/pecl-memcache
+TEST_PHP_ARGS="--show-diff --keep-all -w fails.log" make test