new acb_theta module #1602

Job	Run time
FreeBSD Clang (x0.5)	10m 31s
Alpine Linux, musl, 32-bit (assert, x1.5)	14m 55s
Cygwin GCC (x0.5)	24m 5s
macOS GCC with BLAS (x3)	20m 42s
MinGW GCC (x0.5)	12m 1s
MSVC (x1)	11m 14s
Nemo.jl (temporary branch)	11m 30s
Ubuntu Clang with examples (x5)	13m 18s
Ubuntu GCC, Code Coverage (x10)	21m 43s
Ubuntu GCC, CMake (1x)	6m 46s
Ubuntu GCC with NTL (assert, x2)	9m 7s
	2h 35m 52s

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