Fix regression reported by Michael Esser and Andrew Watson
(independently).

In our recently switch to llvm::raw_ostream (and friends) (I think this
is d934d983692c8952cdb887cbcd59f2df0001b9c0) we forgot to flush the
llvm::raw_string_ostream to the underlying string used for error report
files (e.g. test000001.overshift.err) so we would end up writing an
empty string to error report files.

Also added a test case to catch this.
Merge pull request #133 from delcypher/fix_empty_error_report

Fix regression reported by Michael Esser and Andrew Watson
Fix to avoid warning message taking address of main
Merge pull request #137 from MartinNowack/fix_cxx_standard

Fix to avoid warning message taking address of main
Refactor klee-stats and add simple line chart drawing functionality.
Merge pull request #113 from antiAgainst/klee-stats

klee-stats refactoring and improvement by antiAgainst: "this includes changing from OptionParser to ArgumentParser, rewriting not-pythonic code, respecting PEP8, etc; Adding line chart drawing in klee-stats."
Revert "Patch by Dan Liew: "Improved AutoRegen script so that it supports newer versions of autoconf""

The entire point of this version check in this script is so that configure is
only generated with one exact version of autotools, so that it doesn't get
spurious diffs from people generating it with different versions. This is the
approach used by LLVM, and I'd like to stick to it. Most people don't regenerate
these files, so it falls on the people who do to install the appropriate
versions of the tools.

If we want to change this policy, we should just drop the version checks completely.
Regenerate configure with sanctioned autoconf version.
Do not require <sys/capability.h>, which is Linux specific.
Do not require mallinfo(), which is Linux specific.
Add support for getting memory usage on Darwin.
Tweak the workarounds for multiple definition of PACKAGE_* macros from config.h files.

 - There seems to be a better solution for this by defining a macro prefix, per:

     http://www.gnu.org/software/autoconf-archive/ax_prefix_config_h.html

   but I have no experience with that and it looks like it might involve
   rewriting a bunch of our macro checks.
Regenerate configure.
When building against libc++ (vs libstdcxx), use standard unordered_{map,set} includes.

 - I'm not sure what the status of libstdcxx's c++11 support is. It may be we
   can just move over to <unordered_map> everywhere, but I don't have a Linux
   test machine handy at the moment.
XFAIL LargeReturnTypes.cpp on Darwin, it depends indirectly on using libstdcxx.
Update FloatingPointOps concrete test case for LLVM changes.
Update testingUtils to use printf(), putchar() isn't a known external function anymore.
Update Concrete test Makefile for LLVM changes.
Rewrite ConcreteTest.py to only run one test at a time.
Fix up Concrete Makefile to not remove outputs, so tests can run in parallel.