Merge pull request #2149 from fredrik-johansson/mpoly #1650

Job	Run time
Alpine Linux, musl, 32-bit (assert, x1.5)	14m 9s
MinGW GCC (x0.5)	10m 46s
GCC build regression check (no tests)	1m 8s
macOS-M1, Clang (x3)	7m 46s
MSVC (x1)	10m 11s
Nemo.jl	17m 49s
Ubuntu Clang, BLAS and examples (x5)	13m 0s
Ubuntu GCC, Code Coverage (x10)	28m 57s
Ubuntu GCC with NTL (assert, x2)	8m 11s
	1h 51m 57s

Provide feedback