Consult $HOME rather than calling getpwuid(),

Consult $HOME rather than calling getpwuid(),

Quiting getpwnam(3):

	An application that wants to determine its user’s home
	directory should inspect the value of HOME (rather than the value
	getpwuid(getuid())->pw_dir) since this allows the user to modify
	their notion of "the home directory" during a login session.

Change the function to return const char *, i.e. a pointer to the
environment rather than a copy that must be freed by the caller.
Document that the caller must not modify or free this string and fix
all callers accordingly.