travis-ci: updated ftp.pcre.org to sourceforge mirror. (#1965)

Author: xiaocang

.travis.yml

@@ -67,7 +67,7 @@ before_install:
 
 install:
  - if [ ! -f download-cache/drizzle7-$DRIZZLE_VER.tar.gz ]; then wget -P download-cache http://openresty.org/download/drizzle7-$DRIZZLE_VER.tar.gz; fi
- - if [ ! -f download-cache/pcre-$PCRE_VER.tar.gz ]; then wget -P download-cache https://ftp.pcre.org/pub/pcre/pcre-$PCRE_VER.tar.gz; fi
+ - if [ ! -f download-cache/pcre-$PCRE_VER.tar.gz ]; then wget -P download-cache https://downloads.sourceforge.net/project/pcre/pcre/${PCRE_VER}/pcre-${PCRE_VER}.tar.gz; fi
  - if [ ! -f download-cache/openssl-$OPENSSL_VER.tar.gz ]; then wget -P download-cache https://www.openssl.org/source/openssl-$OPENSSL_VER.tar.gz || wget -P download-cache https://www.openssl.org/source/old/${OPENSSL_VER//[a-z]/}/openssl-$OPENSSL_VER.tar.gz; fi
  - git clone https://github.com/openresty/test-nginx.git
  - git clone https://github.com/openresty/openresty.git ../openresty