clint: Add diagnostics for things like char* foo or (char*)

Asterisk should be preceded by a space except the following cases:

1. `foo[*idx_ptr]`
2. `++*foo` (though I would prefer to write this as `++(*foo)`)
3. `(*foo)->bar`, `if (*p)`
4. `char **foo`
5. `/* comment */`
6. `!*p`

Note: `[^ (*/![]` is followed by `+` to make error position easier to find. It
is not needed to find location of the problem.

clint.py

@@ -2291,6 +2291,11 @@ def CheckSpacing(filename, clean_lines, linenum, nesting_state, error):
     # there's too little whitespace, we get concerned.  It's hard to tell,
     # though, so we punt on this one for now.  TODO.
 
+    match = Search(r'(?:[^ (*/![])+(?<!\+\+|--)\*', line)
+    if match:
+        error(filename, linenum, 'whitespace/operators', 2,
+              'Missing space before asterisk in %s' % match.group(0))
+
     # You should always have whitespace around binary operators.
     #
     # Check <= and >= first to avoid false positives with < and >, then