new genAst as replacement for quote do (#17426)

* new `macros.genAst`: fixes all issues with `quote do`
* add changelog entry
* add workaround for https://github.com/nim-lang/Nim/issues/2465#issuecomment-511076669
* add test for #9607
* add kNoExposeLocalInjects option
* add test case for nested application of genAst
* genAst: automatically call newLit when needed
* allow skipping `{}`: genAst: foo
* add test that shows this fixes #11986
* add examples showing mixin; add examples showing passing types, macros, templates
* move to std/genasts
* improve docs

lib/core/macros.nim

@@ -539,6 +539,7 @@ proc parseStmt*(s: string): NimNode {.noSideEffect.} =
 
 proc getAst*(macroOrTemplate: untyped): NimNode {.magic: "ExpandToAst", noSideEffect.}
   ## Obtains the AST nodes returned from a macro or template invocation.
+  ## See also `genasts.genAst`.
   ## Example:
   ##
   ## .. code-block:: nim
@@ -559,6 +560,8 @@ proc quote*(bl: typed, op = "``"): NimNode {.magic: "QuoteAst", noSideEffect.} =
   ##
   ## A custom operator interpolation needs accent quoted (``) whenever it resolves
   ## to a symbol.
+  ##
+  ## See also `genasts <genasts.html>`_ which avoids some issues with `quote`.
   runnableExamples:
     macro check(ex: untyped) =
       # this is a simplified version of the check macro from the
@@ -1419,7 +1422,7 @@ proc expectIdent*(n: NimNode, name: string) {.since: (1,1).} =
   if not eqIdent(n, name):
     error("Expected identifier to be `" & name & "` here", n)
 
-proc hasArgOfName*(params: NimNode; name: string): bool=
+proc hasArgOfName*(params: NimNode; name: string): bool =
   ## Search `nnkFormalParams` for an argument.
   expectKind(params, nnkFormalParams)
   for i in 1..<params.len: