LibC: add probably functional *printf

I wrote a general printf function that takes an putc function
pointer. We can use this to implement all the printf family
functions. I haven't done thorough testing with this, but it seems
to be functional for the most part

libc/CMakeLists.txt

@@ -5,6 +5,7 @@ project(libc CXX)
 set(LIBC_SOURCES
 	ctype.cpp
 	fcntl.cpp
+	printf_impl.cpp
 	stdio.cpp
 	stdlib.cpp
 	string.cpp