Add lines for adult mosquito population density

Usage

xde_lines_M(MYZ, pars, clrs = "darkblue", llty = 1)

MYZ: a list the output of exDE::parse_deout()
pars: a list that defines an exDE model (e.g., generated by xde_setup())
clrs: a vector of colors
llty: an integer (or integers) to set the lty for plotting