Fix building on Solaris x86-64.

Fix building on Solaris x86-64.

sb-unix:unix-select used macros which expanded into many forms,
limited by sb-unix:fd-setsize, which on Solaris-x86-64 is 65536, as
opposed to 1024 on Linux. This resulted in long compile times which
were likely to exhaust the heap.
Use functions instead of macros.