Rename BlackList class to SpecialCaseList and move it to Transforms/Utils.

Differential Revision: http://llvm-reviews.chandlerc.com/D1089
Introduce a SpecialCaseList ctor which takes a MemoryBuffer to make
it more unit testable, and fix memory leak in the other ctor.

Differential Revision: http://llvm-reviews.chandlerc.com/D1090
Add some SpecialCaseList unit tests.

Differential Revision: http://llvm-reviews.chandlerc.com/D1091
Implement categories for special case lists.

A special case list can now specify categories for specific globals,
which can be used to instruct an instrumentation pass to treat certain
functions or global variables in a specific way, such as by omitting
certain aspects of instrumentation while keeping others, or informing
the instrumentation pass that a specific uninstrumentable function
has certain semantics, thus allowing the pass to instrument callers
according to those semantics.

For example, AddressSanitizer now uses the "init" category instead of
global-init prefixes for globals whose initializers should not be
instrumented, but which in all other respects should be instrumented.

The motivating use case is DataFlowSanitizer, which will have a
number of different categories for uninstrumentable functions, such
as "functional" which specifies that a function has pure functional
semantics, or "discard" which indicates that a function's return
value should not be labelled.

Differential Revision: http://llvm-reviews.chandlerc.com/D1092
Apply BlackList -> SpecialCaseList rename in Clang.

Differential Revision: http://llvm-reviews.chandlerc.com/D1095