Comments of form "// [given x] outputs y" we can check the examples do as expected.

No longer abort ccanlint because a test fails, but you will get a low
score if there are no tests.

(Note: total_score is filled in, even if it's overridden when the test is
 run.  This means that if the prereq fails, that total counts so there is
 still a penalty!)

The heuristics can be hinky, so tell people what we're doing.

A simple C program to generate config.h.  It also saves the compiler and
flags for use by ccanlint (though they have to accept -c and -o).

Warnings about ignored returns, and uninitialized len after case statement.

unsigned char * is allowed to alias, so we use that for byte reversing
rather than uint32_t.  This is portable.

Remove warnings about ignoring pread/pwrite return values.

And initialize tdb before setjmp: with optimization, gcc validly saw this
as NULL and crashed.

A void * could point to anything, but a void ** can't point to any pointer.
So we use a void * and memcpy, which I believe is safe.

Compiling with gcc -O3 added some more warnings, especially about aliasing.

By setting Word_t to size_t we fix some of them, but jmap_@name_firstval
in JMAP_DEFINE_PTRIDX_TYPE we need to use a real size_t rather than lazily
casting our index to a size_t *.

Gcc also spotted taht we used idx[NUM] in test/run-ptridx-type.c; allocate
that and make the usage explicit.

I noticed this when I straced something; we're doing 1-byte writes.
This reduced the time for "make check" from 12m37s to 11m48s.

If you've not got gcc, this is a bit of a lose.  But for everyone else,
it's far simpler.

Doing our own parsing lost a few lines of code, too.

Our coverage is over 99% now.

This was for lockcheck, but that didn't work very well.  Seems like a useful
addition nonetheless.

With correct seed, we could expand hash and break test.

Paul Wayper points out that "or" has a better mental mapping, and more
importantly that this is how Perl's Getopt::Long does it.

I'm still leaving the - and -- in there, for reasons previously articulated
(grep-friendly and harder to get wrong).

In particular, gcc warns about cast from int to pointer.

Instead, directly control write().

%.* => unsigned, not size_t.