FnSubst1.ASM   - GPF error when writing to CODE SEGMENT.

FnSubst2.ASM   - Many debugging code.
               - Writing to CODE SEGMENT works.

FnSubst3.ASM   - Many debugging code.
               - Writing to CODE SEGMENT works.
               - Restoring previous bytes inside CODE SEGMENT works too.

FnSubst4.ASM   - No debugging code anymore, so program is shorter.

FnSubst5.ASM   - RETF  instruction is used instead of  JMP  instruction.

FnSubst6.ASM   - Substituing two functions, using two routines making it all!!
