post beta2 fixes

midb.asm:
exception handler for peripheral 68881 writes into location 0
This is now fixed

midb.asm:
fcmp2fp was defined as $5428, it should be $5438, this has no
material affect since we use a software comparison algorithm anyway.

library.asm
If library in use, call to Expunge has no affect now.

Fixed up Expunge/Close to work properly. Also saved a few bytes
of code.

Expunge now closes the mathieeedoubbas library when it really expunges.
This will allow that library to also expunge.

May 27,1988
Expunge did not set expunge on last close bit if call to Expunge failed
because the library was opened by others.

May 27,1988
Expunge now protected by Forbid/Permit. Needed because Close would
jump into it and Expunge dicks with unprotected data structures.

May 27,1988
If a 68020/68881 was installed this library would initialize the rounding
and exception control modes. This is done by the basic library itself
when it is opened. This code was removed from this library and it now
assumes the OpenLibrary("mathieeedoubbas.library") will do the right thing.

June 13,1988
May 27,1988 introduced bugs. Permit can destroy d0, so moved the loading
of d0 to after the Permit call.
Also the Ext functions were improperly returning seglist when they should
have been returning d0=#0

