[Diffusion] rL232622: Remove many superfluous SmallString::str() calls.

[Ilia K]

This commit broke a OS X build:

  FAILED: /usr/bin/c++   -DCLANG_ENABLE_ARCMT -DCLANG_ENABLE_OBJC_REWRITER -DCLANG_ENABLE_STATIC_ANALYZER -DGTEST_HAS_RTTI=0 -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -std=c++11 -stdlib=libc++ -fPIC -fvisibility-inlines-hidden -Wall -W -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wcovered-switch-default -std=c++11 -fcolor-diagnostics -fno-common -Woverloaded-virtual -fno-strict-aliasing -Wno-nested-anon-types -O3 -DNDEBUG -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk -Itools/clang/lib/StaticAnalyzer/Checkers -I../tools/clang/lib/StaticAnalyzer/Checkers -I../tools/clang/include -Itools/clang/include -Iinclude -I../include    -fno-exceptions -fno-rtti -MMD -MT tools/clang/lib/StaticAnalyzer/Checkers/CMakeFiles/clangStaticAnalyzerCheckers.dir/DereferenceChecker.cpp.o -MF tools/clang/lib/StaticAnalyzer/Checkers/CMakeFiles/clangStaticAnalyzerCheckers.dir/DereferenceChecker.cpp.o.d -o tools/clang/lib/StaticAnalyzer/Checkers/CMakeFiles/clangStaticAnalyzerCheckers.dir/DereferenceChecker.cpp.o -c ../tools/clang/lib/StaticAnalyzer/Checkers/DereferenceChecker.cpp
  ../tools/clang/lib/StaticAnalyzer/Checkers/DereferenceChecker.cpp:165:31: error: conditional expression is ambiguous; 'llvm::StringRef' can be converted to 'SmallString<100>' and vice versa
                    buf.empty() ? BT_null->getDescription() : buf,
                                ^ ~~~~~~~~~~~~~~~~~~~~~~~~~   ~~~
  1 error generated.
  ninja: build stopped: subcommand failed.


/cfe/trunk/lib/StaticAnalyzer/Checkers/DereferenceChecker.cpp:165 here

USERS
  grosbach (Auditor)

http://reviews.llvm.org/rL232622

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