Fix diffusion_matrix compilation on Linux (#863)

Added LBDL to compile diffusion_matrix.c

Author: lfarv

atmat/atmexall.m

@@ -102,7 +102,7 @@ function atmexall(varargin)
 cdir=fullfile(atroot,'atphysics','Radiation');
 compile([alloptions, {passinclude}], fullfile(cdir,'findmpoleraddiffmatrix.c'));
 compile([alloptions, {passinclude}], fullfile(cdir,'FDW.c'));
-compile([alloptions, {passinclude}], fullfile(cdir,'diffusion_matrix.c'));
+compile([alloptions, {passinclude}, LIBDL], fullfile(cdir,'diffusion_matrix.c'));
 
 % RDTs
 cdir=fullfile(atroot,'atphysics','NonLinearDynamics');