Ruby MapScript Exceptions

[jimk]

Improve exception handling in Ruby MapScript. Instead of just returning a generic error, this looks at the most recent ErrorObj and raises the appropriate Ruby exception for

MS_IOERR => IOError
MS_MEMERR => NoMemError
MS_TYPEERR => TypeError
MS_EOFERR => EOFError
MS_CHILDERR => Mapscript::MapServerChildError
all others => Mapscript::MapServerError

With the Exception message set to the result of msGetErrorString().

This is basically porting from Python MapScript to Ruby.

[jimk]

All changes in ./mapscript/ruby/rbmodule.i

Committed revision 11185.

[jimk]

r11185