Remove NSFileHandle category

This category was introduced (96309951f2f34e9c1ec9ea371b7894a230f9e4e2) to avoid repeatedly typing:

    [foo writeData:@"bar" dataUsingEncoding:NSUTF8StringEncoding]];.

However, it has since been superseded by `writeStringToOutput` and `writeStringToError`. So let's remove it and let these methods use the original call above.
Don't use the C++ `not` operator
Use Objective-C boxing for C string pointer types
camelCase local file descriptors variable names
Remove ErrorAndReturn macro

The macro used to be called multiple times before commit 2030fd14327ff463392f83b5a7a3ba1b487d4eed and now this is the only place where it's used, so let's just remove it.
Move ivars declaration to their class extensions

This is really just to make the code styling more similar to the TextMate source.
TMDNibController: Use properties
TMDIncrementalPopUpMenu: Use properties