Use trampolines for all libcalls in engine-universal and engine-dylib

In both of these engines, the compiled code may be loaded in memory far
from the Wasmer runtime which means that libcalls may not be reachable
through the normal relocation types. Instead a trampoline is needed to
allow reaching any address in the 64-bit address space.

In the case of engine-dylib, this is even worse since the symbols are
not exported by the executable without some special linker flags. The
solution here is to manually patch in the addresses at load time into
a data table of function pointers.

lib/compiler-singlepass/src/compiler.rs

@@ -187,7 +187,6 @@ impl Compiler for SinglepassCompiler {
             function_call_trampolines,
             dynamic_function_trampolines,
             None,
-            None,
         ))
     }
 }