Eu adicionei as linhas abaixo no arquivo de repositório: /etc/apt/sources.list
deb http://security.debian.org/ jessie/updates main
deb-src http://security.debian.org/ jessie/updates main
deb http://security.debian.org/ jessie/updates main contrib non-free
deb-src http://security.debian.org/ jessie/updates main contrib non-free
deb http://http.us.debian.org/debian jessie main contrib non-free
Após a atualização: apt-get update
com as linhas adicionadas acima, pude instalar o pacote php5-dev
com sucesso!