Fix a bug introduced in 2019-07-24T21:28:13!eggert@cs.ucla.edu.
* src/fileio.c (file_name_absolute_p):
~/foo is also absolute (Bug#36809).
* test/src/fileio-tests.el (fileio-tests--file-name-absolute-p):
Rename from fileio-tests--no-such-user and add more tests.