Move repositories to 'repos/' subdirectory

This patch changes the top-level directory layout as a preparatory
step for improving the tools for managing 3rd-party source codes.
The rationale is described in the issue referenced below.

Issue #1082

repos/base-nova/src/kernel/target.mk

@@ -0,0 +1,47 @@
+TARGET           = hypervisor
+REQUIRES         = x86 nova
+NOVA_SRC_DIR     = $(REP_DIR)/contrib
+NOVA_BUILD_DIR   = $(BUILD_BASE_DIR)/kernel
+STARTUP_LIB      =
+SRC_CC           = $(sort $(notdir $(wildcard $(NOVA_SRC_DIR)/src/*.cpp)))
+SRC_S            = $(sort $(notdir $(wildcard $(NOVA_SRC_DIR)/src/*.S)))
+INC_DIR          = $(NOVA_SRC_DIR)/include
+CC_OLEVEL        = -Os
+CC_WARN          = -Wall -Wextra -Waggregate-return -Wcast-align -Wcast-qual \
+                   -Wconversion -Wdisabled-optimization -Wformat=2 \
+                   -Wmissing-format-attribute -Wmissing-noreturn -Wpacked \
+                   -Wpointer-arith -Wredundant-decls -Wshadow -Wwrite-strings \
+                   -Wabi -Wctor-dtor-privacy -Wno-non-virtual-dtor \
+                   -Wold-style-cast -Woverloaded-virtual -Wsign-promo \
+                   -Wframe-larger-than=64 -Wlogical-op -Wstrict-null-sentinel \
+                   -Wstrict-overflow=5 -Wvolatile-register-var
+CC_OPT          += -pipe \
+                   -fdata-sections -fomit-frame-pointer -freg-struct-return \
+                   -freorder-blocks -funit-at-a-time -fno-exceptions -fno-rtti \
+                   -fno-stack-protector -fvisibility-inlines-hidden \
+                   -fno-asynchronous-unwind-tables -std=gnu++0x 
+ifeq ($(filter-out $(SPECS),32bit),)
+CC_OPT          += -mpreferred-stack-boundary=2 -mregparm=3
+else
+ifeq ($(filter-out $(SPECS),64bit),)
+CC_OPT          += -mpreferred-stack-boundary=4 -mcmodel=kernel -mno-red-zone
+else
+$(error Unsupported environment)
+endif
+endif
+
+git_version      = $(shell cd $(NOVA_SRC_DIR) && (git rev-parse HEAD 2>/dev/null || echo 0) | cut -c1-7)
+CXX_LINK_OPT     = -Wl,--gc-sections -Wl,--warn-common -Wl,-static -Wl,-n -Wl,--defsym=GIT_VER=0x$(call git_version)
+LD_TEXT_ADDR     = # 0xc000000000 - when setting this 64bit compile fails because of relocation issues!! 
+LD_SCRIPT_STATIC = hypervisor.o
+
+$(TARGET): hypervisor.o
+
+hypervisor.o: $(NOVA_SRC_DIR)/src/hypervisor.ld
+	$(VERBOSE)$(CC) $(INCLUDES) -MP -MMD -pipe $(CC_MARCH) -xc -E -P $< -o $@
+
+clean cleanall:
+	$(VERBOSE)rm -rf $(NOVA_BUILD_DIR)
+
+vpath %.cpp $(NOVA_SRC_DIR)/src
+vpath %.S $(NOVA_SRC_DIR)/src