LibC: Rewrite environ handling

environ is only allocated on heap when you insert new variables.

environment variables are only `free`'d if they are `malloc`'d by libc

userspace/libraries/LibC/CMakeLists.txt

@@ -4,6 +4,7 @@ set(LIBC_SOURCES
 	ctype.cpp
 	dirent.cpp
 	dlfcn.cpp
+	environ.cpp
 	errno.cpp
 	fcntl.cpp
 	fenv.cpp