examples/modint.jl: add ::IO dispatch to show and showcompact.
examples/bubblesort.jl: define the BubbleSort algorithm as an example.
Various deprecation improvements.

 - only warn once per unique deprecation message
 - support randi and randival with deprecation warnings

Other rand* functions are not really deprecated – they're just not
supported anymore. These warnings point the direction to where to go
for the equivalent functionality.