Install libpcre3-dev for Linux builds

This package contains the required PCRE library development files and
may be already installed, as is apparently the case for amd64 systems,
but also may not be, as when using s390x architecture.

Author: vadz

Tools/travis-linux-install.sh

@@ -13,7 +13,7 @@ if [[ -n "$GCC" ]]; then
 	travis_retry sudo apt-get install -qq g++-$GCC
 fi
 
-travis_retry sudo apt-get -qq install libboost-dev
+travis_retry sudo apt-get -qq install libboost-dev libpcre3-dev
 
 WITHLANG=$SWIGLANG