Build optlink with masm 9 or 10 and with dmc-tools instead of SLR

- build libs with dmc's lib
- masm (v9 or v10) complained about a number of "mov AL,errorCode" which had to be changed to AX (I guess it would not assume an external to fit into a byte)
- add a number of ridiculous "BYTE PTR" modifiers
- do not build loadx.exe

To build, set environment variable DM (if not \dm), add dmc\bin to the path and run build_optlink.bat.