Search for guards in C API specs too #200

Job	Run time
Check ruby/spec still passes with MSpec changes	1s
test (3.3)	1s
test (3.0)	1s
test (3.1)	1s
test (3.2)	1s
test (2.7)	1s
test (ruby-head)	15m 1s
test (2.6)	15m 1s
test (3.4)	1s
test (truffleruby-head)	1s
	30m 10s

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