Fix bug in Ada attributes lexing

The Ada lexer allows whitespace between the apostrophe and the
attribute text, but processAttribute does not handle this.  This patch
fixes the problem and introduces a regression test.

gdb/ada-lex.l

@@ -227,7 +227,7 @@ false		{ return FALSEKEYWORD; }
 
         /* ATTRIBUTES */
 
-{TICK}[a-z][a-z_]+ { BEGIN INITIAL; return processAttribute (yytext+1); }
+{TICK}[a-z][a-z_]+ { BEGIN INITIAL; return processAttribute (yytext); }
 
 	/* PUNCTUATION */
 
@@ -663,6 +663,11 @@ attributes[] = {
 static int
 processAttribute (const char *str)
 {
+  gdb_assert (*str == '\'');
+  ++str;
+  while (isspace (*str))
+    ++str;
+
   for (const auto &item : attributes)
     if (strcasecmp (str, item.name) == 0)
       return item.code;

gdb/testsuite/gdb.ada/formatted_ref.exp

@@ -70,13 +70,15 @@ proc test_p_x_addr { var addr } {
     global gdb_prompt
 
     foreach attr {access unchecked_access unrestricted_access} {
-	set test "print/x $var'$attr"
-	gdb_test_multiple $test $test {
-	    -re "\\$\[0-9\]+ = $addr.*$gdb_prompt $" {
-		pass $test
-	    }
-	    -re "\\$\[0-9\]+ = 0x\[a-f0-9+\]+.*$gdb_prompt $" {
-		fail "$test (prints unexpected address)"
+	foreach space {"" "  "} {
+	    set test "print/x $var'$space$attr"
+	    gdb_test_multiple $test $test {
+		-re "\\$\[0-9\]+ = $addr.*$gdb_prompt $" {
+		    pass $test
+		}
+		-re "\\$\[0-9\]+ = 0x\[a-f0-9+\]+.*$gdb_prompt $" {
+		    fail "$test (prints unexpected address)"
+		}
 	    }
 	}
     }