DC_Rbp, Remove Breakpoint

IN:  BHL = pointer to breakpoint

OUT: Fc=0, success and IX=handle

     Fc=1, failure and A=error
        RC_Fail, error during removal
        RC_Eof, cannot find debug handle
        RC_Use, breakpoint is running

Registers affected after return:

    A.BCDEHL/..IY same
    .F....../IX.. different