Makefile and minor fixes

[aropan]

I used this Makefile for correctly work (sorry that I do not pull request):

PROTO_SRC := <path-to-proto-files>
PROTO_DST := ${PROTO_SRC}/build
PROTO_FILES := $(wildcard ${PROTO_SRC}/*.proto)
LUA_FILES := $(addprefix ${PROTO_DST}/,$(notdir $(PROTO_FILES:.proto=_pb.lua)))

all: ${PROTO_DST} ${LUA_FILES}

${PROTO_DST}:
    mkdir -p ${PROTO_DST}

${PROTO_DST}/%_pb.lua: ${PROTO_SRC}/%.proto
    protoc -I ${PROTO_SRC} $< --lua_out ${PROTO_DST}

    # fixed require with bracket end line
    sed "s/^\(local.*require.*\))$$/\1/" -i $@

    # fixed message from extrenal file
    grep '^local [^=]*_pb = require' $@ | \
        awk '{print $$2}' | \
        while read r; do sed -i "s/ = module.$${r}_/ = $${r}./i" $@; done