Improved error handling

Turns off default GSL error handler so that it doesn't crash Julia when an error happens. Instead, throws a GSL_ERROR

Newly generated wrappers also catch errors and throws GSL_ERROR when appropriate.
use GSL_ERROR
Improved wrapper generator

Has some heuristics for guessing what outputs are needed and specifying & on the ccall line
Fixes generation of gsl_rand_dir_2d*
Updated generated wrappers