expect "export" in test configs
CVE-2013-6401: Change hash function, randomize hashes

Thanks to Florian Weimer and Eric Sesterhenn for reporting, reviewing
and testing.
Document json_object_seed()
jansson 2.6
Merge branch '2.6'
Oops, ATOMIC_ACQ_REL is not a correct memmodel for __atomic_store_n
Merge branch '2.6'
Fix feature checks to use correct __ATOMIC flags
Make valgrind happy
Fix feature checks to use correct __ATOMIC flags
Make valgrind happy
Merge branch '2.6'
Three fixes for hashtable seeding on Windows

First, wrap "advapi32.dll" into the TEXT() macro. If UNICODE is defined,
GetModuleHandle() redirects to GetModuleHandleW(), which excepts a wchar_t*
UTF-16 parameter, thus causing a compile error. TEXT() prefixes the string
literal with L in this case, and does nothing otherwise.

Second, make sure that CryptGenRandom() is actually called through the function
pointer retrieved by the call to GetProcAddress() above.

And third, replace _getpid() with the equivalent and more ubiquitous Win32 API
function GetCurrentProcessId(). Since _getpid() is not exported by all C
runtimes on Windows (most notably the Driver Development Kit), using it might
introduce previously unneeded runtime dependencies. GetCurrentProcessId(), on
the other hand, has been available in kernel32.dll since at least Windows 95,
just like the other API functions used in this code (GetModuleHandle() and
GetProcAddress()).
Allow to mix JSON_STRICT with optional keys

On unpack, one may want to mix `JSON_STRICT` and optional keys by using
a format like `{s:i,s?o!}`. Unfortunately, this fails the stric test
with `-1 object item(s) left unpacked` error when the second key is not
specified.

To fix that, we iter on each key and we check if we have successfully
unpacked them. This is less efficient than the previous method but it
brings correctness.
Micro-optimization for JSON_STRICT when no optional key is used

The previous commit introduced a loop on all input keys to check the
strict mode. We can avoid this if we don't expect an optional key. In
this case, we fallback to the previous method to compare the length of
the set of expected keys and the length of the parsed keys.
Add new autotools-generated files to .gitignore

Additionally, `/jansson_private_config.h.in` is also added as well as
"build" directory for those of us who like to use an out-of-tree build
system.
Merge pull request #162 from nmlgc/master

Three fixes for hashtable seeding on Windows
Merge pull request #163 from vincentbernat/fix/unpack-mix-optional-and-strict

Fix unpack when mixing strict mode and optional keys
Merge pull request #164 from vincentbernat/fix/gitignore

Add new autotools-generated files to .gitignore
Merge pull request #162 from nmlgc/master

Three fixes for hashtable seeding on Windows