Update ax_lua.m4

[pnorman]

Updates ax_lua.m4 to 2015-01-30 version from git.savannah.gnu.org, serial 36.

Fixes #188. Replaces #222

This might improve FreeBSD support - have to test still.

Checked on a Ubuntu 14.04 VM. As the entire point of autoconf is to work across a variety of systems, more checks are welcome - in fact essential.

[lonvia]

Works ok on Debian stable(wheezy) and testing(jessie).

[pnorman]

Doesn't fix finding Lua on FreeBSD

checking for a Lua interpreter with version >= 5.0... lua52
checking for lua52... /usr/local/bin/lua52
checking for lua52 version... 5.2
checking for lua52 platform... unknown
checking for lua52 script directory... ${prefix}/share/lua/5.2
checking for lua52 module directory... ${exec_prefix}/lib/lua/5.2
checking if LUA_VERSION is defined... yes
checking lua.h usability... no
checking lua.h presence... no
checking for lua.h... no
checking lualib.h usability... no
checking lualib.h presence... no
checking for lualib.h... no
checking lauxlib.h usability... no
checking lauxlib.h presence... no
checking for lauxlib.h... no
checking luaconf.h usability... no
checking luaconf.h presence... no
checking for luaconf.h... no
checking for Lua headers in... /usr/local/include/lua52
checking lua.h usability... yes
checking lua.h presence... yes
checking for lua.h... yes
checking lualib.h usability... yes
checking lualib.h presence... yes
checking for lualib.h... yes
checking lauxlib.h usability... yes
checking lauxlib.h presence... yes
checking for lauxlib.h... yes
checking luaconf.h usability... yes
checking luaconf.h presence... yes
checking for luaconf.h... yes
checking for Lua header version... 5.2
checking if Lua header version matches 5.2... yes
checking if LUA_VERSION is defined... yes
checking for library containing exp... -lm
checking for library containing dlopen... none required
checking for library containing lua_load... no
configure: WARNING: cannot find Lua libs

When I manually specify the Lua information I get

...
checking if LUA_VERSION is defined... yes
checking for library containing lua_load... none required

I'd still say it works on FreeBSD - nothing is any worse, and it does allow the configure line to be trimmed to LUA_LIB=pkg-config --libs lua-5.2 ./configure --without-lockfree

[tomhughes]

Configures OK on Fedora 21:

checking for a Lua interpreter with version >= 5.0... lua
checking for lua... /usr/bin/lua
checking for lua version... 5.2
checking for lua platform... unknown
checking for lua script directory... ${prefix}/share/lua/5.2
checking for lua module directory... ${exec_prefix}/lib/lua/5.2
checking if LUA_VERSION is defined... yes
checking lua.h usability... yes
checking lua.h presence... yes
checking for lua.h... yes
checking lualib.h usability... yes
checking lualib.h presence... yes
checking for lualib.h... yes
checking lauxlib.h usability... yes
checking lauxlib.h presence... yes
checking for lauxlib.h... yes
checking luaconf.h usability... yes
checking luaconf.h presence... yes
checking for luaconf.h... yes
checking for Lua header version... 5.2
checking if Lua header version matches 5.2... yes
checking if LUA_VERSION is defined... yes
checking for library containing exp... -lm
checking for library containing dlopen... -ldl
checking for library containing lua_load... -llua-5.2

Build is failing, but that seems to be a protobuf issue, not lua.