Change the JIT to compile eagerly by default as agreed in
http://llvm.org/PR5184, and beef up the comments to describe what both options
do and the risks of lazy compilation in the presence of threads.

llvm-svn: 85295
diff --git a/llvm/lib/ExecutionEngine/ExecutionEngine.cpp b/llvm/lib/ExecutionEngine/ExecutionEngine.cpp
index 16808a7..c61ab87 100644
--- a/llvm/lib/ExecutionEngine/ExecutionEngine.cpp
+++ b/llvm/lib/ExecutionEngine/ExecutionEngine.cpp
@@ -49,7 +49,7 @@
 ExecutionEngine::ExecutionEngine(ModuleProvider *P)
   : EEState(*this),
     LazyFunctionCreator(0) {
-  LazyCompilationDisabled = false;
+  CompilingLazily         = false;
   GVCompilationDisabled   = false;
   SymbolSearchingDisabled = false;
   DlsymStubsEnabled       = false;