fix Issue 13664 - Grammar does not allow @<template_instance> UDAs
Update exception-safe doc

Replace scope classes with structs.
Improve formatting.
Merge pull request #693 from ntrel/scope-class

Update exception-safe doc
Replace scope class with struct
Replace `length` in slices by `$`
Merge pull request #696 from ntrel/length-dollar

Replace `length` in slices by `$`
Merge pull request #694 from ntrel/scope-guard

Replace scope class with struct
Added new type alias syntax as a preference

Added elaboration based on comments received

Fix syntax errors
Added instructions for building a single ddoc file without needing to clone other repositories
Merge pull request #698 from JinShil/patch-2

Added instructions for building a single ddoc file without needing to clone other repositories
macros.ddoc
Merge pull request #701 from aG0aep6G/macros.ddoc

macros.ddoc
Merge pull request #683 from 9rnsr/fix13664

Issue 13664 - Grammar does not allow @<template_instance> UDAs
Merge pull request #682 from JinShil/patch-1

Added new type alias syntax as a preference
Document difference between type constructors & storage classes.
Replace "type constructor" with "type qualifier".