fix bugs of softice.ASM, "Execution Timing", and "Guard Pages".

Thank you for your useful samples.
I found the following problems of your samples.
- softice.ASM does not set a exception handler. 
  And, Flat Assembler generates "icebp" from "int1" mnemonic.
- Execution Timing tests calculate "initial - end".
- Guard Pages test does not jump to the allocated pages.

I fixed softice.ASM and Execution Timing tests.
And, I reimplemented Guard Pages test using assembly language.
If you please, pull my commit.