set aside fixnums in GCL Major Section:  ACL2-BUILT-INS
(Allocate-fixnum-range fixnum-lo fixnum-hi) causes Gnu Common
Lisp (GCL) to create a persistent table for the integers between
fixnum-lo and fixnum-hi (both bounds inclusive). This table is
referenced first when any integer is boxed and the existing box
in the table is used if the integer is in bounds. This can speed
up GCL considerably by avoiding wasteful fixnum boxing. Here,
fixnum-lo and fixnum-hi should be fixnums. On 32-bit machines it
would be good for them to be of type (signed-byte 30), with
fixnum-lo <= fixnum-hi.