doc+cmake: LLVM 3.3 is preferred

Change-Id: Ie480efbe5ffd2f0a59da7f185bba80a5355251f9

cmake/FindLLVM.cmake

-find_program(LLVMCONFIG NAMES llvm-config llvm-config-3.1)
+find_program(LLVMCONFIG NAMES llvm-config llvm-config-3.3 llvm-config-3.2 llvm-config-3.1)
 
 if( NOT LLVMCONFIG )
   message(FATAL_ERROR "llvm-config not found, try installing llvm-dev llvm")

doc/how-to-build.txt

@@ -15,6 +15,11 @@ Required for Fail*:
  - AspectC++ (ag++, ac++): AspectC++ 1.1 or newer is known to work and can be
    obtained from http://www.aspectc.org; nightlies can be downloaded from
    http://akut.aspectc.org
+ - optional:
+   * LLVM 3.3 (needed for several importers in tools/import-trace)
+     (compiles/links with 3.1 or 3.2, but fails to properly import information
+     from ELF binaries not compiled with -ffunction-sections)
+
 
 Required for the Bochs simulator backend:
 **********************************************************************

src/core/util/CMakeLists.txt

@@ -63,7 +63,7 @@ add_library(fail-util ${SRCS})
 add_dependencies(fail-util fail-comm)
 target_link_libraries(fail-util ${PROTOBUF_LIBRARY} ${Boost_LIBRARIES} ${LIB_IBERTY} )
 
-option(BUILD_LLVM_DISASSEMBLER "Build the llvm based disassembler (exactly llvm 3.1 required)" OFF)
+option(BUILD_LLVM_DISASSEMBLER "Build the LLVM-based disassembler (LLVM 3.3 preferred, for 3.1 and 3.2 read doc/how-to-build.txt)" OFF)
 if (BUILD_LLVM_DISASSEMBLER)
   add_subdirectory(llvmdisassembler)
 endif (BUILD_LLVM_DISASSEMBLER)