Added cpplint.py output format for eclipse

Patch by mcasas@chromium.org
CR: https://codereview.chromium.org/16140002/

diff --git a/cpplint/cpplint.py b/cpplint/cpplint.py
index 159dbbb..4d15272 100755
--- a/cpplint/cpplint.py
+++ b/cpplint/cpplint.py
@@ -875,6 +875,9 @@
     if _cpplint_state.output_format == 'vs7':
       sys.stderr.write('%s(%s):  %s  [%s] [%d]\n' % (
           filename, linenum, message, category, confidence))
+    elif _cpplint_state.output_format == 'eclipse':
+      sys.stderr.write('%s:%s: warning: %s  [%s] [%d]\n' % (
+          filename, linenum, message, category, confidence))
     else:
       sys.stderr.write('%s:%s:  %s  [%s] [%d]\n' % (
           filename, linenum, message, category, confidence))
@@ -3970,8 +3973,8 @@
     if opt == '--help':
       PrintUsage(None)
     elif opt == '--output':
-      if not val in ('emacs', 'vs7'):
-        PrintUsage('The only allowed output formats are emacs and vs7.')
+      if not val in ('emacs', 'vs7', 'eclipse'):
+        PrintUsage('The only allowed output formats are emacs, vs7 and eclipse.')
       output_format = val
     elif opt == '--verbose':
       verbosity = int(val)