fix cfunction escaping bug (#566)

Author: stevengj

src/Compat.jl

@@ -1914,7 +1914,7 @@ end
 # 0.7.0-DEV.4762
 @static if !isdefined(Base, Symbol("@cfunction"))
     macro cfunction(f, rt, tup)
-        :(Base.cfunction($f, $rt, Tuple{$tup...}))
+        :(Base.cfunction($(esc(f)), $(esc(rt)), Tuple{$(esc(tup))...}))
     end
     export @cfunction
 end

test/runtests.jl

@@ -1749,6 +1749,14 @@ let ptr = @cfunction(+, Int, (Int, Int))
     @test ptr != C_NULL
     @test ccall(ptr, Int, (Int, Int), 2, 3) == 5
 end
+# issue #565
+issue565(x) = x + 1
+const Issue565 = Int
+let bar() = @cfunction(issue565, Issue565, (Issue565,)), ptr = bar()
+    @test ptr isa Ptr{Cvoid}
+    @test ptr != C_NULL
+    @test ccall(ptr, Int, (Int,), 2) === 3
+end
 
 # 0.7.0-DEV.5278
 @test something(nothing, 1) === 1