Some test program cleanup.

- Simplify Makefile by allowing to use suffix '_tcp' to denote the requirement to link against TCP-capable IP65 lib.
- Remove 'test' or 'test_' prefix from test program names - every program in 'test' is a test program.
- Have some more test programs switch to lower case charset on the C64.
- I'm no Ruby guy so don't rely on Ruby for building disk images.