Lua: Ensure liblua.dylib is created

Adding versionless soft link in INSTALL_LIB to allow linking with -llua (see
homebrew issue Homebrew#6350 for an example) (Related to name change in commit
9228a05).

Fixes Homebrew#7642.
Fixes Homebrew#6648.
Closes Homebrew#7561.
Closes Homebrew#7517.
Closes Homebrew#6235.

Signed-off-by: Charlie Sharpsteen <source@sharpsteen.net>

Library/Formula/lua.rb

@@ -64,11 +64,12 @@ def install
  TO_MAN= lua.1 luac.1
 
  # Lua version and release.
-@@ -64,6 +64,7 @@ install: dummy
+@@ -64,6 +64,8 @@ install: dummy
  	cd src && $(INSTALL_DATA) $(TO_INC) $(INSTALL_INC)
  	cd src && $(INSTALL_DATA) $(TO_LIB) $(INSTALL_LIB)
  	cd doc && $(INSTALL_DATA) $(TO_MAN) $(INSTALL_MAN)
 +	ln -s -f liblua.5.1.4.dylib $(INSTALL_LIB)/liblua.5.1.dylib
++	ln -s -f liblua.5.1.dylib $(INSTALL_LIB)/liblua.dylib
 
  ranlib:
  	cd src && cd $(INSTALL_LIB) && $(RANLIB) $(TO_LIB)