checkpatch: fix regressions in "fix handling of leading spaces"

The patch "checkpatch: fix handling of leading spaces" added checks for
leading spaces on lines, but this introduces regressions.  Firstly it does
not correctly detect when we are in a comment.  Secondly it does not allow
for preprocessor command spacing.  Finally it does not allow for label
indentation which is required to be less than one tab.  Fix these up:

Signed-off-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -1459,10 +1459,13 @@ sub process {
 		}
 
 # check for spaces at the beginning of a line.
-		if ($rawline =~ /^\+ / && $rawline !~ /\+ +\*/)  {
+# Exceptions:
+#  1) within comments
+#  2) indented preprocessor commands
+#  3) hanging labels
+		if ($rawline =~ /^\+ / && $line !~ /\+ *(?:$;|#|$Ident:)/)  {
 			my $herevet = "$here\n" . cat_vet($rawline) . "\n";
-			WARN("please, no space for starting a line, \
-				excluding comments\n" . $herevet);
+			WARN("please, no spaces at the start of a line\n" . $herevet);
 		}
 
 # check we are in a valid C source file if not then ignore this hunk