Bug 1155760 - remove obsolete JAVA_{GEN_DIR,DIST_DIR,IFACES_PKG_NAME} definitions; r=nalexander

These definitions appear to have been added to support generating Java
interfaces from xpidl interface files.  Since we don't support doing
that anymore, we don't need these definitions, either.

config/config.mk

@@ -298,11 +298,6 @@ MY_RULES	:= $(DEPTH)/config/myrules.mk
 #
 CCC = $(CXX)
 
-# Java macros
-JAVA_GEN_DIR  = _javagen
-JAVA_DIST_DIR = $(DEPTH)/$(JAVA_GEN_DIR)
-JAVA_IFACES_PKG_NAME = org/mozilla/interfaces
-
 INCLUDES = \
   -I$(srcdir) \
   -I. \