Support `Manticore` db in syntax

It was support of Manticore.table, but `Manticore`.table fired an error.
Now both variants work.

That closes #3566 (gitlab)

src/sphinxql.l

@@ -200,7 +200,7 @@ FLOAT_CONSTANT      {INT}\.{INT}?{EXP}?|{INT}?\.{INT}{EXP}|{INT}{EXP}
 "WHERE"				{ YYSTOREBOUNDS; return TOK_WHERE; }
 "WITHIN"			{ YYSTOREBOUNDS; return TOK_WITHIN; }
 
-"MANTICORE."
+"MANTICORE."        |
 "`MANTICORE`."      { YYSTOREBOUNDS; return TOK_MANTICORE; }
 
 "!="				{ YYSTOREBOUNDS; return TOK_NE; }

src/sphinxql.y

@@ -307,7 +307,7 @@ idxname:
 
 identidx:
 	 idxname
-	 | TOK_MANTICORE idxname
+	 | TOK_MANTICORE idxname {$$ = $2;}
 	;
 
 one_index: