Fixes warnings when installing with OSX/homebrew

[seryl]

As shown below, fixes the following:

josh@kiva: Desktop/zklua> make
gcc -c `pkg-config --cflags lua5.1` -fPIC -O2  zklua.c
Package lua5.1 was not found in the pkg-config search path.
Perhaps you should add the directory containing `lua5.1.pc'
to the PKG_CONFIG_PATH environment variable
No package 'lua5.1' found
zklua.c:291:1: warning: control reaches end of non-void function [-Wreturn-type]
}
^
zklua.c:312:1: warning: control reaches end of non-void function [-Wreturn-type]
}
^
zklua.c:689:1: warning: control may reach end of non-void function [-Wreturn-type]
}
^
zklua.c:697:1: warning: control reaches end of non-void function [-Wreturn-type]
}
^
zklua.c:705:1: warning: control reaches end of non-void function [-Wreturn-type]
}
^
5 warnings generated.

[seryl]

Still seeing:

Cloning into 'zklua'...
remote: Counting objects: 21, done.
remote: Compressing objects: 100% (19/19), done.
remote: Total 21 (delta 1), reused 17 (delta 1)
Receiving objects: 100% (21/21), 25.32 KiB | 0 bytes/s, done.
Resolving deltas: 100% (1/1), done.
Checking connectivity... done.
export MACOSX_DEPLOYMENT_TARGET=10.5; gcc -O2 -fPIC -I/usr/local/opt/lua/include -c zklua.c -o zklua.o
export MACOSX_DEPLOYMENT_TARGET=10.5; gcc -bundle -undefined dynamic_lookup -all_load -o zklua.so -L/usr/local/opt/lua/lib zklua.o -lzklua
ld: library not found for -lzklua
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Error: Build error: Failed compiling module zklua.so

[seryl]

Actual make currently works, and the library installs properly