#474 iem_matrix: implicit declaration of function ‘sqrt’

[Hans-Christoph Steiner]

warnings that could cause problems with 64-bit builds:

pd/auto-build/pd-extended/externals/pdp/include -DUNIX -Dunix -DDL_OPEN -fPIC -o "/home/pd/auto-build/pd-extended/externals/iem/iem_matrix/src/matrix_orthogonal.o" -c "/home/pd/auto-build/pd-extended/externals/iem/iem_matrix/src/matrix_orthogonal.c"
/home/pd/auto-build/pd-extended/externals/iem/iem_matrix/src/matrix_orthogonal.c: In function ‘matrix_orthogonal_matrix’:/home/pd/auto-build/pd-extended/externals/iem/iem_matrix/src/matrix_orthogonal.c:109: warning:
/home/pd/auto-build/pd-extended/externals/iem/iem_matrix/src/matrix_orthogonal.c:109: warning: incompatible implicit declaration of built-in function ‘sqrt’