Route all output through premake.out() to simplify interception and overriding.

Fix a related bug in the C++ makefile generator.

src/actions/make/make_cpp.lua

@@ -41,7 +41,7 @@
 	}
 
 	function make.cpp.generate(prj)
-		io.eol("\n")
+		premake.eol("\n")
 		premake.callarray(make, cpp.elements.makefile, prj)
 	end
 

src/base/premake.lua

@@ -196,11 +196,9 @@
 ---
 
 	function premake.outln(s)
+		premake.out(s)
 		if not _captured then
-			io.write(s)
 			io.write(_eol or "\n")
-		else
-			table.insert(_captured, s)
 		end
 	end