Deprecate using && and || within at-dot expressions

Giving us space to allow lowering this to `.&&` and `.||` in the future. Ref #5187.

Author: mbauman

base/broadcast.jl

@@ -850,6 +850,11 @@ function __dot__(x::Expr)
            Meta.isexpr(x.args[1], :call) # function or macro definition
         Expr(x.head, x.args[1], dotargs[2])
     else
+        if x.head == :&& || x.head == :||
+            Base.depwarn("""
+                using $(x.head) expressions in @. is deprecated; in the future it will
+                become elementwise. Break the expression into smaller parts instead.""", ())
+        end
         head = string(x.head)
         if last(head) == '=' && first(head) != '.'
             Expr(Symbol('.',head), dotargs...)

base/deprecated.jl

@@ -82,7 +82,7 @@ function depwarn(msg, funcsym)
         _id=(frame,funcsym),
         _group=:depwarn,
         caller=caller,
-        maxlog=1
+        maxlog=funcsym === () ? nothing : 1
     )
     nothing
 end