CLIENT-4752 polymorphic map types jdk8 #256

Job	Run time
make-matrix	6s
build-8.1.0.3_2-8.1.0.3_2 / build-bouncycastle-8.1.0.3_2-8 / build	2m 34s
build-8.1.0.3_2-8.1.0.3_2 / build-gnu-8.1.0.3_2-8 / build	2m 18s
build-8.1.1.0_1-8.1.1.0_1 / build-bouncycastle-8.1.1.0_1-8 / build	2m 31s
build-8.1.1.0_1-8.1.1.0_1 / build-gnu-8.1.1.0_1-8 / build	2m 25s
	9m 54s

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