Replace most invocations of fail keyword with die! macro
rustdoc: Convert astsrv to pipes
DO NOT COMMIT
Remove fail keyword from lexer & parser and clean up remaining calls to
fail

Fix merge conflicts - Issue 4524
rustdoc: Convert page_pass to pipes
Long lines
Revert "DO NOT COMMIT"

This reverts commit 76679c1f91fc68134c850b2d77ff2b83b32a108f.
Merge pull request #4720 from jbclements/syntactic-cleanup

Syntactic cleanup
Merge remote-tracking branch 'nickdesaulniers/issue4524' into nocomm1