Fixed the --warnings_as_errors output.

As @ottojo points in #1 this option counted warnings as errors, but
never printed the warnings.
Now the code does what the option says: warnings are converted to
errors. Not just counted as errors, but also printed as errors.
I think this is more coherent with the name of the option.

src/eeschema_do

@@ -217,6 +217,8 @@ def eeschema_parse_erc(erc_file, warning_as_error=False):
 
     cont = False
     is_err = False
+    global errs
+    global wrns
     for line in lines:
         m = re.search(r'^ErrType\((\d+)\): (.*)', line)
         if m:
@@ -246,6 +248,8 @@ def eeschema_parse_erc(erc_file, warning_as_error=False):
     warnings = m.group(3)
 
     if warning_as_error:
+        errs += wrns
+        wrns = []
         return int(errors) + int(warnings), 0
     return int(errors), int(warnings)