FEAT/CHANGE: allowing @name to be a valid email! type

For a compatibility with Red language and also because it may be useful in dialects.
Although `@name` is not a valid real email according RFC, one can construct invalid email values in many ways and so in real use for email apps, there should be a real additional email validation anyway.

Related to: Oldes/Rebol-issues#1962

Author: Oldes

src/core/l-scan.c

@@ -782,12 +782,12 @@
         }
 
     case LEX_CLASS_SPECIAL:
-        if (HAS_LEX_FLAG(flags, LEX_SPECIAL_AT) && *cp != '<') return TOKEN_EMAIL;
+        if (HAS_LEX_FLAG(flags, LEX_SPECIAL_AT) && *cp != '<') return TOKEN_EMAIL; // for case like: %61@b which is actually: a@b
     next_ls:
         switch (GET_LEX_VALUE(*cp)) {
 
-        case LEX_SPECIAL_AT:
-            return -TOKEN_EMAIL;
+        case LEX_SPECIAL_AT:            /* @username */
+            return TOKEN_EMAIL;
 
         case LEX_SPECIAL_PERCENT:       /* %filename */
             cp = scan_state->end;

src/tests/units/lexer-test.r3

@@ -22,6 +22,13 @@ Rebol [
 
 ===end-group===
 
+===start-group=== "Email"
+	--test-- "valid `emails`"
+		--assert email? load {name@where}
+		--assert email? load {@name} ;@@ https://github.com/Oldes/Rebol-issues/issues/1962
+
+===end-group===
+
 ===start-group=== "SIGN before POUND char (issue #2319)"
 ;@@ https://github.com/rebol/rebol-issues/issues/2319
 	--test-- "sign-before-pound-1"	--assert  [- #"a"] = (load {-#"a"})