MEDIUM: lua: lua integration in the build and init system.

This is the first step of the lua integration. We add the useful
files in the HAProxy project. These files contains the main
includes, the Makefile options and empty initialisation function.
Is is the LUA skeleton.
diff --git a/Makefile b/Makefile
index 052c082..a48e9b3 100644
--- a/Makefile
+++ b/Makefile
@@ -28,6 +28,7 @@
 #   USE_VSYSCALL         : enable vsyscall on Linux x86, bypassing libc
 #   USE_GETADDRINFO      : use getaddrinfo() to resolve IPv6 host names.
 #   USE_OPENSSL          : enable use of OpenSSL. Recommended, but see below.
+#   USE_LUA              : enable Lua support.
 #   USE_FUTEX            : enable use of futex on kernel 2.6. Automatic.
 #   USE_ACCEPT4          : enable use of accept4() on linux. Automatic.
 #   USE_MY_ACCEPT4       : use own implemention of accept4() if glibc < 2.10.
@@ -74,6 +75,8 @@
 #   PCRE_INC       : force the include path to libpcre ($PCREDIR/inc)
 #   SSL_LIB        : force the lib path to libssl/libcrypto
 #   SSL_INC        : force the include path to libssl/libcrypto
+#   LUA_LIB        : force the lib path to lua
+#   LUA_INC        : force the include path to lua
 #   IGNOREGIT      : ignore GIT commit versions if set.
 #   VERSION        : force haproxy version reporting.
 #   SUBVERS        : add a sub-version (eg: platform, model, ...).
@@ -557,6 +560,12 @@
 endif
 endif
 
+ifneq ($(USE_LUA),)
+OPTIONS_CFLAGS  += -DUSE_LUA $(if $(LUA_INC),-I$(LUA_INC))
+OPTIONS_LDFLAGS += $(if $(LUA_LIB),-L$(LUA_LIB)) -llua -lm
+OPTIONS_OBJS    += src/hlua.o
+endif
+
 ifneq ($(USE_PCRE)$(USE_STATIC_PCRE)$(USE_PCRE_JIT),)
 # PCREDIR is used to automatically construct the PCRE_INC and PCRE_LIB paths,
 # by appending /include and /lib respectively. If your system does not use the