Split warn.py into multiple files

* Split warning patterns into *_warn_patterns.py
* Split project list into android_project_list.py
* Split out the Severity class, to be changed later
* Split core of warn.py into warn_common.py and
  leave only platform dependent code in warn.py.
  This allows the core logic be used with different
  parallel processing libraries.
* Old warn.py just calls -m warn.warn.

Test: path_to_build/tools/warn.py build.log
Test: warn.py --url=http://cs/android --separator='?l=' build.log > warnings.html
Change-Id: I6734e4472a21018cd5ce06d549f6dbca24f4de54
diff --git a/tools/warn/severity.py b/tools/warn/severity.py
new file mode 100644
index 0000000..bb23f2c
--- /dev/null
+++ b/tools/warn/severity.py
@@ -0,0 +1,47 @@
+#
+# Copyright (C) 2019 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Severity levels and attributes."""
+
+
+class Severity(object):
+  """Severity levels and attributes."""
+  # numbered by dump order
+  FIXMENOW = 0
+  HIGH = 1
+  MEDIUM = 2
+  LOW = 3
+  ANALYZER = 4
+  TIDY = 5
+  HARMLESS = 6
+  UNKNOWN = 7
+  SKIP = 8
+  range = range(SKIP + 1)
+  attributes = [
+      # pylint:disable=bad-whitespace
+      ['fuchsia',   'FixNow',    'Critical warnings, fix me now'],
+      ['red',       'High',      'High severity warnings'],
+      ['orange',    'Medium',    'Medium severity warnings'],
+      ['yellow',    'Low',       'Low severity warnings'],
+      ['hotpink',   'Analyzer',  'Clang-Analyzer warnings'],
+      ['peachpuff', 'Tidy',      'Clang-Tidy warnings'],
+      ['limegreen', 'Harmless',  'Harmless warnings'],
+      ['lightblue', 'Unknown',   'Unknown warnings'],
+      ['grey',      'Unhandled', 'Unhandled warnings']
+  ]
+  colors = [a[0] for a in attributes]
+  column_headers = [a[1] for a in attributes]
+  headers = [a[2] for a in attributes]
+