Retire support for old environment variables.

We have deprecated the old environment variable names for quite a
while and now it's time to remove them.  Gone are:

    SHA1_FILE_DIRECTORIES AUTHOR_DATE AUTHOR_EMAIL AUTHOR_NAME
    COMMIT_AUTHOR_EMAIL COMMIT_AUTHOR_NAME SHA1_FILE_DIRECTORY

Signed-off-by: Junio C Hamano <junkio@cox.net>

init-db.c

@@ -226,7 +226,7 @@ int main(int argc, char **argv)
 	/*
 	 * Set up the default .git directory contents
 	 */
-	git_dir = gitenv(GIT_DIR_ENVIRONMENT);
+	git_dir = getenv(GIT_DIR_ENVIRONMENT);
 	if (!git_dir) {
 		git_dir = DEFAULT_GIT_DIR_ENVIRONMENT;
 		fprintf(stderr, "defaulting to local storage area\n");