HD: fix type of 2Pi variable used #551

Job	Run time
build-all-debug-single	3m 49s
build-postlib-release	11m 40s
build-drivers-release	5m 11s
build-all-debug	7m 30s
build-test-uadriver-debug	2m 20s
rtest-module-drivers	4m 30s
rtest-modules-debug	11m 11s
build-fastfarm-release	12m 52s
build-interfaces-release	4m 59s
build-openfast-release	5m 2s
rtest-interfaces	3m 33s
rtest-OF	15m 46s
rtest-OF-5MW_Land_AeroMap	1m 17s
rtest-OF-5MW_Land_BD_DLL_WTurb	2m 28s
rtest-OF-5MW_OC3Mnpl_DLL_WTurb_WavesIrr	2m 8s
rtest-OF-5MW_OC3Trpd_DLL_WSt_WavesReg	5m 22s
rtest-OF-5MW_OC4Jckt_DLL_WTurb_WavesIrr_MGrowth	2m 38s
rtest-OF-5MW_OC4Semi_WSt_WavesWN	2m 0s
rtest-OF-linearization	4m 33s
rtest-OF-simulink	11m 16s
rtest-FF	2m 59s
	2h 3m 4s

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