Cheaper frame introspection

More debugging tips.

clang-3.7 support

Some small documentation

Not sure how we ended up with the '-1' everywhere.

And also detect attempts to compile on a 32-bit system and
quickly give a nice error message -- fixes #1018.

This splits up the handling of deopts and normal frame introspection (e.g. for a traceback).
We have to add to nearly all call sites frame introspection which makes it very important that it does not introduce much overhead over a normal call instruction.
By always storing the user visible variables into a vregs array (layout the same as in the interpreter/bjit) we can make introspection cheaper.
Frame introspection only needs to access user facing variables therefore we don't have to generate extra bytes for spilling variables which get clobbered in the callee because all values we need to access are inside the vregs array.
This let's use remove the 95byte overhead and reduces the stackmap size.
It adds a slight cost of maintaining the vregs array but we were already doing some of this work before with our manual spilling with the additional benefit of faster frame introspection.

The deopts case stays pretty much the same with the exception that we don't add the user visible vars to the stackmap because they are already in the vreg.
We could reduce the overhead by implementing a special "deopt()" function in asm which stores and restores all variables thereby we would not have to manualy spill the registers when filling the deopt IC.
Alternatively we could handle it inside llvm by either switching to a stackmap intrinsic which already supports this case or adding it it does not exist...
But I think it's not worth it because deopts should be uncommen...

Based on recent issues I've encountered working on running the
NumPy test suite.

move ICSetupInfo before PatchpointInfo in anticipation for accessing ICSetupInfo inside the PatchpointInfo

Changing the INSTALLING instructions. 

Test file for paste (and py.test) modules

Fix build error caused by missing 'override's.

Add a clang libTooling example

Update "roadmap" in readme

Surprisingly hard to get the build to work.  I feel like no one must use
libTooling for out-of-tree projects.  Also, the binary can only be run from
the directory in which it would have been placed for an in-tree project.

It was going to be a refcount discipline checker, but I'm not sure that's
a good use of time right now.  I want to check it in though so that we have it.

- add small 0.5 blurb
- add 0.4 blog post link
- reverse order (latest release first)

microbenchmarks for the presentation

add float_repr_style to sys module and enable test_strtod

Some improvements that let test_fractions could pass.

Add two attribute to str that let test_string pass.

Support CMake 3.3+

I guess our hack for pre-3.3 doesn't work in 3.3, but thankfully
we can include both the pre-3.3 workaround and the actual 3.3+ fix,
and it looks like cmake will end up doing the right thing in both cases.