Memory leak with TracePoint on bmethod

	[Bug #20194]

	When disabling the TracePoint on bmethod, the hooks list is not freed.

	For example:

	    obj = Object.new
	    obj.define_singleton_method(:foo) {}
	    bmethod = obj.method(:foo)
	    tp = TracePoint.new(:return) {}

	    10.times do
	      100_000.times do
	        tp.enable(target: bmethod) {}
	      end

	      puts `ps -o rss= -p #{$$}`
	    end

	Before:

	    18208
	    22832
	    26528
	    29728
	    34000
	    37776
	    40864
	    44400
	    47680
	    51504

	After:

	    16688
	    17168
	    17168
	    17248
	    17696
	    17760
	    17824
	    17824
	    17856
	    17920
	---
	 test/ruby/test_settracefunc.rb | 13 +++++++++++++
	 vm_trace.c                     |  1 +
	 2 files changed, 14 insertions(+)