lal/lib/tools/TriggerInterpolate.h: use LAL COMPLEX16 types

Detailed Description

This fixes up !1282 (merged) to use LAL COMPLEX16 types in the header lal/lib/tools/TriggerInterpolate.h instead of double _Complex.

LAL's COMPLEX8/COMPLEX16 have been equivalent to C99's float/double complex for a long time. Moreover, when LAL headers are processed by a non-C99/C++ compiler, COMPLEX8/COMPLEX16 will map to binary-equivalent types from GSL. This is how LAL's C99 headers can be used to compile C++ wrappers for Octave. In short, public LAL headers should always use COMPLEX8/COMPLEX16.

LAL also defines crect(), cpolar() in LALAtomicDatatypes.h so I've removed the custom implementations.

cc @leo-singer @jolien-creighton

API Changes

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Justification for Backwards Incompatible Changes

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Review Status

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