Fix wcwidth import and match safeWcswidth to its documented behavior
Fix wcwidth import and match safeWcswidth to its documented behavior

Previously vty_mk_wcwidth was being imported with the wrong type causing
the -1 return value to be mapped to the wrong Int value.

Additionally safeWcswidth was using the unsafe character width function
and only ensuring that the final result was non-negative.

jtdaugherty/vty,jtdaugherty/vty,jtdaugherty/vty