SDB 1.6

• Added a RuntimeExecutable configuration variable. Look here for information on how to use it.
• Added indirection to ensure that Mono.Posix is only loaded on platforms where it's needed.
• EntryPointNotFoundException is now also handled when trying to load libedit.
• Fixed an incorrect format string in the catch add command output.
• Removed some duplicate code that caused confusing watch command output.
• A more accurate error message is now printed if an expression is valid but evaluation of it is not supported.
• Removed the explicit cecil dependency.
• Bumped the debugger-libs dependency to mono/debugger-libs@66fa04f.
• Bumped the nrefactory dependency to icsharpcode/NRefactory@0607a4a.