VB -> C#: private partial methods do not compile

[jrmoreno1]

• Added unit test to SpecialConversionTests (not MethodStatementTests as there is no statements) -ISymbolExtensions.cs
  • CanHaveMethodBody & IsPartialMethodDefinition
  • Added check for IsPartialDefinition

#1097

Problem

Partial method declarations are including a body, which makes them partial method IMPLEMENTATIONS without declarations and so the resulting conversion does not compile

Solution

• Changed the code as little as possible, I think it fits in with the existing code, could be broken up into multiple (shorter) lines, and negative pattern matching could probably be used, but didn't want to change too much.
• Change to IsPartialMethodDefinition is unnecessary for this, not sure it should be included or not.
• There is a test for problem, but there's not a test for the other end of it (i.e. that it correctly converts partial implementations, but I didn't have a problem with those).
• At least one test covering the code changed

[jrmoreno1]

@GrahamTheCoder : no test results have changed, but I did add a unit test for it. Not sure it's where you'll want it.