Assorted minor bug fixes and cleanups.
Require a C++ 11 compiler to build.
Initial version of the JIT.

Compiles the bodies of frequently run functions, where the compiler simply
generates native code to call back into the interpreter.
Add a .clang-format file that matches the existing CXXR style fairly closely.

As of clang v3.4, clang-format doesn't break lines quite as well as humans,
so this should be considered a useful tool to help maintain a consistent style,
but we shouldn't automatically reformat all code yet.
Run jit code files through clang-format.
Update autoconf built files.
Add missing @LLVM_LDFLAGS@ to src/main/Makefile.in
Disable byte-compile-packages by default.  It causes errors in the JIT code.
Automatically generate the IR for the runtime module at compile time using
clang.
Refactoring.  Move the functions that generate code into a compiler class and ad
a CompilerContext class to hold any configuration settings or state that the
compiler cares about.
Reduce the amount of memory leaks in the JIT code.
Optimized local symbol lookups.

In order to lookup symbols efficiently, we use a frame whose layout is
determined at JIT compilation time.  The code that evaluates symbols then takes
advantage of that information when consulting the local frame.
Rename files to better match their contents.
Fix incorrect capitalization of 'BuiltInFunction'.
Build fixes
Temporarily disable use of CompiledFrames due to bugs.
Match attributes on virtual function override.
Assorted minor bug fixes and cleanups.
Require a C++ 11 compiler to build.
Initial version of the JIT.

Compiles the bodies of frequently run functions, where the compiler simply
generates native code to call back into the interpreter.