Solvers and solver-specific parameters are specified by AbstractMathProgSolver objects, which are provided by particular solver packages. For example, the Clp package exports a ClpSolver object, which can be passed to linprog as follows:
using Clp linprog([-1,0],[2 1],'<',1.5, ClpSolver())
Options are passed as keyword arguments, for example, ClpSolver(LogLevel=1). See the Clp, Cbc, GLPKMathProgInterface, and Gurobi packages for more information.