[test] Fix dependency on compiler behavior for a couple of tests

[test] Fix dependency on compiler behavior for a couple of tests

A couple of tests for System.Reflection.MethodBody assumed the code generated
by the compiler will be the same as the one generated by Mono's MCS. However,
when the code is built by CSC in release mode (version that comes with VS2015
was tested) the optimizations remove locals required by the old version of the
tests. Also, CSC orders the locals differently to MCS and that breaks one of
the tests which relied on the declaration order.
Another difference is that CSC and MCS type a certain local variable differently.
The variable being a byte* in source code is output in IL as such by MCS, but CSC
outputs an int8& - a by-ref type.
The tests are built by VS but they are executed by Mono on Android and so the
differences come up as errors.
This commit fixes both issues by working around the differences.

Fixes https://bugzilla.xamarin.com/show_bug.cgi?id=33370 when it is included in XA