depot_tools: modify cpplint.py to allow CPPLINT.cfg overrides
depot_tools: modify cpplint.py to allow CPPLINT.cfg overrides

Added the ability to provide CPPLINT.cfg files to provide
linter message filters per sub-directory and special exclusion
rules. Each file can have instructions like:

filter=-build/include_order,+build/include_alpha
exclude_files=.*\.cc

The above disables build/include_order warning and enables
build/include_alpha as well as excludes all .cc from being
processed by linter, in the current directory (where the .cfg
file is located) and all sub-directories.

Related CL: https://chromium-review.googlesource.com/#/c/209384/

BUG=chromium:395296
TEST=ran cpplint.py on a bunch of directories in platform2/

Review URL: https://codereview.chromium.org/406373002

git-svn-id: fd409f4bdeea2bb50a5d34bb4d4bfc2046a5a3dd@285999 0039d316-1c4b-4281-b951-d872f2087c98

cpanelli/-git-clone-https-chromium.googlesource.com-chromium-tools-depot_tools,airtimemedia/depot_tools,fracting/depot_tools,Midrya/chromium,azureplus/chromium_depot_tools,Neozaru/depot_tools,SuYiling/chrome_depot_tools,michalliu/chromium-depot_tools,fanjunwei/depot_tools,airtimemedia/depot_tools,ajohnson23/depot_tools,disigma/depot_tools,michalliu/chromium-depot_tools,xuyuhan/depot_tools,withtone/depot_tools,duanwujie/depot_tools,smikes/depot_tools,duanwujie/depot_tools,eatbyte/depot_tools,hsharsha/depot_tools,gcodetogit/depot_tools,SuYiling/chrome_depot_tools,azureplus/chromium_depot_tools,azunite/chrome_build,fracting/depot_tools,azureplus/chromium_depot_tools,kaiix/depot_tools,aleonliao/depot_tools,withtone/depot_tools,smikes/depot_tools,Phonebooth/depot_tools,aleonliao/depot_tools,npe9/depot_tools,CoherentLabs/depot_tools,chinmaygarde/depot_tools,Neozaru/depot_tools,npe9/depot_tools,G-P-S/depot_tools,duongbaoduy/gtools,smikes/depot_tools,fanjunwei/depot_tools,primiano/depot_tools,airtimemedia/depot_tools,liaorubei/depot_tools,cpanelli/-git-clone-https-chromium.googlesource.com-chromium-tools-depot_tools,smikes/depot_tools,Neozaru/depot_tools,npe9/depot_tools,disigma/depot_tools,G-P-S/depot_tools,eatbyte/depot_tools,fanjunwei/depot_tools,ajohnson23/depot_tools,G-P-S/depot_tools,mlufei/depot_tools,azunite/chrome_build,gcodetogit/depot_tools,primiano/depot_tools,liaorubei/depot_tools,mlufei/depot_tools,sarvex/depot-tools,mlufei/depot_tools,npe9/depot_tools,Midrya/chromium,Phonebooth/depot_tools,Phonebooth/depot_tools,hsharsha/depot_tools,eatbyte/depot_tools,gcodetogit/depot_tools,duongbaoduy/gtools,Neozaru/depot_tools,eatbyte/depot_tools,sarvex/depot-tools,smikes/depot_tools,kaiix/depot_tools,azunite/chrome_build,HackFisher/depot_tools,sarvex/depot-tools,cpanelli/-git-clone-https-chromium.googlesource.com-chromium-tools-depot_tools,xuyuhan/depot_tools,fracting/depot_tools,michalliu/chromium-depot_tools,xuyuhan/depot_tools,ajohnson23/depot_tools,chinmaygarde/depot_tools,xuyuhan/depot_tools,Midrya/chromium,withtone/depot_tools,hsharsha/depot_tools,duongbaoduy/gtools,aleonliao/depot_tools,Phonebooth/depot_tools,CoherentLabs/depot_tools,primiano/depot_tools,sarvex/depot-tools,HackFisher/depot_tools,SuYiling/chrome_depot_tools,G-P-S/depot_tools,HackFisher/depot_tools,Neozaru/depot_tools,duanwujie/depot_tools,liaorubei/depot_tools,michalliu/chromium-depot_tools,kaiix/depot_tools,airtimemedia/depot_tools,liaorubei/depot_tools,chinmaygarde/depot_tools,HackFisher/depot_tools,disigma/depot_tools,fanjunwei/depot_tools