Add performance* to default global tidy checks.

* This enables 5 performance related checks:
    performance-faster-string-find
    performance-for-range-copy
    performance-implicit-cast-in-loop
    performance-unnecessary-copy-initialization
    performance-unnecessary-value-param
* Recognize these new warnings in warn.py.

Bug: http://b/27779618
Change-Id: I7af3fdc262dd44db90d3b62eb37c5eac5a2eaa01
Test: build with WITH_TIDY=1 and run warn.py with build.log