vf_fingerprint: use aligned_alloc instead of posix_memalign

I was assuming posix_memalign was the most portable function to use, but
MinGW does not provide it for some reason. Switch to C11 aligned_alloc()
which someone suggested was provided by MinGW (but actually isn't,
someone probably confused it with the incompatible _aligned_malloc),
and add a configure check.

Even though it turned out that MinGW doesn't provide it, the function
is slightly more elegant than posix_memalign(), so stay with it.

wscript

@@ -213,6 +213,11 @@ main_dependencies = [
             check_statement('stdatomic.h',
                 'atomic_int_least64_t test = ATOMIC_VAR_INIT(123);'
                 'atomic_fetch_add(&test, 1)'))
+    }, {
+        # C11; technically we still support C99
+        'name': 'aligned_alloc',
+        'desc': 'C11 aligned_alloc()',
+        'func': check_statement('stdlib.h', 'aligned_alloc(1, 1)'),
     }, {
         'name': 'atomics',
         'desc': 'stdatomic.h support or slow emulation',
@@ -386,6 +391,7 @@ iconv support use --disable-iconv.",
         'func': check_pkg_config('rubberband', '>= 1.8.0'),
     }, {
         'name': '--zimg',
+        'deps': 'aligned_alloc',
         'desc': 'libzimg support (for vf_fingerprint)',
         'func': check_pkg_config('zimg', '>= 2.9'),
     }, {