Add ant targets to get warnings info.

A set of ant targets to allow capturing the build output, effectively
grepping through it to find javac warnings from source files, then
outputting a teamcity info file containing the number.

Change-Id: I54e1ea72c9f7ae39565defb8caf52bf99f5ed941
Reviewed-on: http://gerrit.dmdirc.com/3125
Reviewed-by: Greg Holmes <greg@dmdirc.com>
Automatic-Compile: DMDirc Build Manager