genopinit: Split init_all_optabs [PR113575].

genopinit: Split init_all_optabs [PR113575].

init_all_optabs initializes > 10000 patterns for riscv targets.  This
leads to pathological situations in dataflow analysis (which can occur
with many adjacent stores).
To alleviate this this patch makes genopinit split the init_all_optabs
function into several init_optabs_xx functions that each initialize 1000
patterns.

With this change insn-opinit.cc's compilation time is reduced from 4+
minutes to 1:30 and memory consumption decreases from 1.2G to 630M.

gcc/ChangeLog:

	PR other/113575

	* genopinit.cc (main): Split init_all_optabs into functions
	of 1000 patterns each.