Recommend compiling tutorials with debugging symbols

So that introspection works for them.
Sanitize compiled function name when jitting

There was a problem where functions with names like f[8] were not being found
in the compiled module for older llvms.
Remove use of c++11 method.
moved error for too large buffers

In 32-bit mode it was triggering during the multiply and producing an
internal error. Now we do the multiplies in 64-bits and check each
intermediate result instead, which mirrors what Halide does at runtime.