Fix bug #77361 (configure fails on 64-bit AIX when opcache enabled)

Fix bug #77361 (configure fails on 64-bit AIX when opcache enabled)

In f9048300123, support for GNU Hurd was added to the opcache and
the configure check to ensure the opcache knows the flock struct
layout prior to building was changed check for two cases: BSD layout
and Linux layout. All the existing hard-coded cases in
ZendAccelerator.h follow these two cases, except for 64-bit AIX.
This means that even though building on 64-bit AIX would work,
the configure script refuses to continue.

Add a new configure check for the 64-bit AIX case and a new
compiler definition HAVE_FLOCK_AIX64. Now that all the cases are
covered, simplify the ifdef logic around these three HAVE_FLOCK_*
macros:
- The macOS and the various BSD flavors fall under HAVE_FLOCK_BSD
- Linux, HP-UX, GNU Hurd, 32-bit AIX, and SVR4 environments
  fall under HAVE_FLOCK_LINUX
- 64-bit AIX falls under HAVE_FLOCK_AIX64

The only difference between the existing HAVE_FLOCK_LINUX and
the hard-coded Linux/HP-UX/Hurd case is that the latter
initialized the 5th member to 0, but since the C standard already
says that un-initialized members will be initialized to 0,
it's effectively the same.