Enclose code in documentation in backticks
base64: backticks for code in documentation
bigint: backticks for code in documentation
bitv: backticks for code in documentation
syntax: Fix wrong span on ObsoleteEmptyImpl
syntax: Fix wrong span on ObsoleteMode
syntax: Fix wrong span on trait fn visibility

Fixes #9348.
Add 'continue' as a synonym for 'loop'
Add 'continue' keyword to emacs, vim, gedit, kate
auto merge of #9504 : brson/rust/continue, r=alexcrichton
auto merge of #9523 : huonw/rust/kud1ing-docs, r=huonw

Collation of @kud1ing's work in #9511, #9512, #9513 and #9518.
auto merge of #9525 : klutzy/rust/obsolete-span-fix, r=alexcrichton