h5xxx: Rename machine to h5000.

h5xxx: Rename machine to h5000.
* Use naming scheme consistent with other iPaq devices, where "series" name
is used.
* h5000 is series consisting of h5100, h5400, and h5500 models, each having
common architecture, but slightly different builtin peripherals. Each model
may also have few marketing nicknames, differing in last digit (sometimes 2
last digits).
* Closes #1586.
* Approved by Koen Kooi.