Revert "Faster build if we don't fork the ANTLR task"

Revert "Specify input and library directories for in-process execution of ANTLR Tool"

This reverts commits 3d13177b38d241ef8bcb06c161e54db7a8070ba9 and c2aa783e51e8a451339e833a862ed96d8e545225.
Ant build.xml: look for ANTLR 3 library in lib folder, download from antlr.org if missing. Remove unnecessary build.properties.
Ant build.xml: allow user settings in user.build.properties
Ant build.xml: rename antlr3.gen.dir property to build.antlr3.dir
Ant build.xml: Move mkdir task to antlr3 target, where the grammars are actually compiled
Ant build.xml: use macro to simplify calls to the tool
Ant build.xml: improved up-to-date checks, remove need to pass "-make" to the ANTLR 3 tool