doc: remove misleading/confusing info

We have to specify the module and the function name in the example where
the module shares a crate with the executable as well, so remove the
redundant (and potentially confusing) mention.
librustc: Restrict transmute intrinsicck to just rust-intrinsic fn's.
Add tests to make sure intrinsicck doesn't apply to non-intrinsic fn's.
Use cargo run in more places
auto merge of #16724 : tshepang/rust/misleading, r=brson

We have to specify the module and the function name in the example where
the module shares a crate with the executable as well, so remove the
redundant (and potentially confusing) mention.
auto merge of #16751 : luqmana/rust/tr, r=alexcrichton

Fixes #15562.
auto merge of #16752 : MatejLach/rust/more_cargorun, r=steveklabnik

Use cargo run as much as possible...
debuginfo: Allow to activate GDB pretty printers in autotests.
debuginfo: Add GDB pretty printers for structs and enums.
debuginfo: Emit different autotest debugger scripts depending on GDB version.
debuginfo: Improve GDB version handling in compiletest tool