[make] better modularize the build system

-Each module's rules.mk defines a seperate linkage unit. Each
module can have a private set of CFLAGS, DEFINES, INCLUDES, and so
forth.
-Files to be compiled are now added by source, not object.

Most rules.mk files can be converted easily by following these steps:

1) add 'MODULE := $(LOCAL_DIR)' near the top of the file
2) change OBJS += to MODULE_SRCS += and list source files instead of .os
3) add 'include make/module.mk' at the bottom of the file

See make/module.mk for directions.

make/module.mk

@@ -0,0 +1,97 @@
+
+# modules
+#
+# args:
+# MODULE : module name (required)
+# MODULE_SRCS : list of source files, local path (required)
+# MODULE_DEPS : other modules that this one depends on
+# MODULE_DEFINES : #defines local to this module
+# MODULE_OPTFLAGS : OPTFLAGS local to this module
+# MODULE_COMPILEFLAGS : COMPILEFLAGS local to this module
+# MODULE_CFLAGS : CFLAGS local to this module
+# MODULE_CPPFLAGS : CPPFLAGS local to this module
+# MODULE_ASMFLAGS : ASMFLAGS local to this module
+# MODULE_SRCDEPS : extra dependencies that all of this module's files depend on
+
+# MODULE_ARM_OVERRIDE_SRCS : list of source files, local path that should be force compiled with ARM (if applicable)
+
+# the minimum module rules.mk file is as follows:
+#
+# LOCAL_DIR := $(GET_LOCAL_DIR)
+# MODULE := $(LOCAL_DIR)
+#
+# MODULE_SRCS := $(LOCAL_DIR)/at_least_one_source_file.c
+#
+# include make/module.mk
+
+# test for old style rules.mk
+ifneq ($(MODULE_OBJS),)
+$(warning MODULE_OBJS = $(MODULE_OBJS))
+$(error MODULE $(MODULE) is setting MODULE_OBJS, change to MODULE_SRCS)
+endif
+ifneq ($(OBJS),)
+$(warning OBJS = $(OBJS))
+$(error MODULE $(MODULE) is probably setting OBJS, change to MODULE_SRCS)
+endif
+
+MODULE_SRCDIR := $(MODULE)
+MODULE_BUILDDIR := $(call TOBUILDDIR,$(MODULE_SRCDIR))
+
+# add the listed module deps to the global list
+MODULES += $(MODULE_DEPS)
+
+#$(info module $(MODULE))
+#$(info MODULE_SRCDIR $(MODULE_SRCDIR))
+#$(info MODULE_BUILDDIR $(MODULE_BUILDDIR))
+#$(info MODULE_DEPS $(MODULE_DEPS))
+#$(info MODULE_SRCS $(MODULE_SRCS))
+
+# generate a per-module config.h file
+MODULE_CONFIG := $(MODULE_BUILDDIR)/module_config.h
+
+$(MODULE_CONFIG): MODULE_DEFINES:=$(MODULE_DEFINES)
+$(MODULE_CONFIG): configheader
+	$(call MAKECONFIGHEADER,$@,MODULE_DEFINES)
+
+GENERATED += $(MODULE_CONFIG)
+
+MODULE_COMPILEFLAGS += --include $(MODULE_CONFIG)
+
+MODULE_SRCDEPS += $(MODULE_CONFIG)
+
+# include the rules to compile the module's object files
+include make/compile.mk
+
+# MODULE_OBJS is passed back from compile.mk
+#$(info MODULE_OBJS = $(MODULE_OBJS))
+
+# build a ld -r style combined object
+MODULE_OBJECT := $(call TOBUILDDIR,$(MODULE_SRCDIR).mod.o)
+$(MODULE_OBJECT): $(MODULE_OBJS)
+	@$(MKDIR)
+	@echo linking $@
+	$(NOECHO)$(LD) -r $^ -o $@
+
+# track all the objects built
+ALLOBJS += $(MODULE_OBJS)
+
+# make the rest of the build depend on our output
+ALLMODULE_OBJS := $(ALLMODULE_OBJS) $(MODULE_OBJECT)
+
+# empty out any vars set here
+MODULE :=
+MODULE_SRCDIR :=
+MODULE_BUILDDIR :=
+MODULE_DEPS :=
+MODULE_SRCS :=
+MODULE_OBJS :=
+MODULE_DEFINES :=
+MODULE_OPTFLAGS :=
+MODULE_COMPILEFLAGS :=
+MODULE_CFLAGS :=
+MODULE_CPPFLAGS :=
+MODULE_ASMFLAGS :=
+MODULE_SRCDEPS :=
+MODULE_CONFIG :=
+MODULE_OBJECT :=
+MODULE_ARM_OVERRIDE_SRCS :=