* Error -> Defect for defects
The distinction between Error and Defect is subjective,
context-dependent and somewhat arbitrary, so when looking at an
exception, it's hard to guess what it is - this happens often when
looking at a `raises` list _without_ opening the corresponding
definition and digging through layers of inheritance.
With the help of a little consistency in naming, it's at least possible
to start disentangling the two error types and the standard lib can set
a good example here.
* allow defects to be caught even for --exceptions:goto (WIP)
* implemented the new --panics:on|off switch; refs https://github.com/nim-lang/RFCs/issues/180
* new implementation for integer overflow checking
* produce a warning if a user-defined exception type inherits from Exception directly
* applied Timothee's suggestions; improved the documentation and replace the term 'checked runtime check' by 'panic'
* fixes#13627
* don't inherit from Exception directly
of recent Clang and GCC >= 5.0.
Maybe it's better that it's optional after all. GCC's code with builtin
overflow checks seems to be a bit slower actually, while Clang's is 3
times faster.
This only works with recent Clang and GCC 5.0.
Currently it doesn't work because __has_builtin can't be defined.
This is totally ugly. But we can't reliably detect whether we can use
the builtins from Nim, especially with cross-compiling where the user
may be using an older compiler version. Switching this on/off manually
with a define seems weird as well, this should work automatically.
