Use log4j-1.2 instead of log4j-1.2.16

/usr/share/java/log4j-1.2.jar is a symlink to the newest release of
log4j 1.2 installed on the system. Our systems have log4j-1.2.17
installed, but not log4j-1.2.16, causing the build to fail.

This change adds the symlink instead of the 1.2.16 jar file to avoid
this problem

Change-Id: I2a9c9b2c504231847e59a6a10e3b20728db15088
Use JAVA_HOME from environment if present

This change causes the rules file to set JAVA_HOME to OpenJDK only if
the variable is not already set in the environment.

A change to follow this one will allow the build to depend on any
compatible JDK rather than on OpenJDK specifically.

Change-Id: I9c238d2de67300891dc8274b97b2b3ee0e5d79ca
Depend on any java7 jre/jdk

Change the Build-Depends and Depends directives of the package to refer
to the relevant Java distribution that OpenJDK provides as an alternative,
rather than directly only to OpenJDK.

This allows any compatible Java distribution to fulfill the dependency
without placing a strict requirement on OpenJDK.

$ dpkg -I openjdk-7-jdk_7u55-2.4.7-1ubuntu1_amd64.deb | grep Provides
 Provides: java-compiler, java-sdk, java2-sdk, java5-sdk, java6-sdk, java7-jdk

$ dpkg -I openjdk-7-jre_7u55-2.4.7-1ubuntu1_amd64.deb | grep Provides
 Provides: java-runtime, java2-runtime, java5-runtime, java6-runtime, java7-runtime

Change-Id: I8c9b480521487a5a19f7813340472d99a88a112a
Merge "Depend on any java7 jre/jdk" into debian
Merge "Use JAVA_HOME from environment if present" into debian
Merge branch 'debian' of ssh://gerrit.wikimedia.org:29418/operations/debs/kafka