Move ElfLoader from libart-compiler-llvm to libart.

Due to the fact that we are going to use ElfLoader
in OatFile, CommonTest, and Compiler, it won't be a
good idea to keep ElfLoader as backend specific class.
Thus, we should move ElfLoader to libart.

Change-Id: I3d264266b3771eaa935b1768be1937797f57f7d7
diff --git a/src/compiler_llvm/elf_loader.cc b/src/compiler_llvm/elf_loader.cc
index ccb02ad..60fce0b 100644
--- a/src/compiler_llvm/elf_loader.cc
+++ b/src/compiler_llvm/elf_loader.cc
@@ -52,7 +52,7 @@
 
   if (executable == NULL) {
     LOG(WARNING) << "Failed to load ELF"
-                 << " image: " << elf_image.begin()
+                 << " image: " << static_cast<const void*>(elf_image.begin())
                  << " size: " << elf_image.size();
     return false;
   }