v0.45.0

Most relevant commits:

• compiler/parser: fix error message parsing '{% end foo bar %}'
• compiler/parser: improve missing end statement error
• compiler: add the 'raw' statement
• cmd/scriggo,test/compare: support parsing of Go devel versions
• runtime: handle conversions from []T to *[N]T
• compiler/parser: fix panic parsing '{{ }}' in a declaration context
• compiler/parser: improve non-allowed macro declaration error
• compiler/parser: don't parse short show statement with an option
• compiler/checker: don't allow slicing of format types
• compiler/checker: fix impossible type assertion at compile-time
• templates/builtin: add 'Time.IsZero' method
• compiler/checker: fix error 'extra expression in const declaration'
• compiler/checker: fix position of errors in const declaration
• compiler/checker: fix error message on assignment mismatch