gcc 2.96 != gcc 2.96

[Ronald G. Minnich]

gcc 2.96 on redhat 8.0 compiles linuxbios just fine. gcc 2.96 on redhat 
7.3 gets an error on that pirq change I made recently.

I have now put in, tested, and committed the following patch, let me know
if this helps:

#if GCC_VERSION < 3000
        struct irq_info slots[1];
#else
        struct irq_info slots[];
#endif

Compiles now on my redhat 7.3

ron