add string param type so that the string format of the paramter can be passed to the plugin for further processing.
Merge pull request #98 from liuhongchao/add-string-param-type

add string param type so that the string format of the paramter can be p...
Pop to buffer when listing interpreted modules interactively
Play it safe in case formatting a variable binding fails
Safer return value handling for plugin calls
Fix pretty-printing pids in edts_debug variable list
Do xref analysis even if compilation fails
Remove all xref errors when analysis result is empty