Use ADDITIONAL_HEADER_DIRS in all LLVM CMake projects.

This allows IDEs to recognize the entire set of header files for
each of the core LLVM projects.

Differential Revision: http://reviews.llvm.org/D7526
Reviewed By: Chris Bieneman

llvm-svn: 228798
diff --git a/llvm/lib/Bitcode/Reader/CMakeLists.txt b/llvm/lib/Bitcode/Reader/CMakeLists.txt
index f614c9f..62954f2 100644
--- a/llvm/lib/Bitcode/Reader/CMakeLists.txt
+++ b/llvm/lib/Bitcode/Reader/CMakeLists.txt
@@ -2,6 +2,9 @@
   BitReader.cpp
   BitcodeReader.cpp
   BitstreamReader.cpp
+
+  ADDITIONAL_HEADER_DIRS
+  ${LLVM_MAIN_INCLUDE_DIR}/llvm/Bitcode
   )
 
 add_dependencies(LLVMBitReader intrinsics_gen)