Avoid build failure when building without -fsanitize=address.
* src/lisp.h (UNALIGNED_LOAD_SIZE): Only use the sanitizer version of
the macro when USE_SANITIZER_UNALIGNED_LOAD is defined, avoiding link
errors when building without -fsanitize=address.
Address sanitizer may miss memory bugs that happen during unaligned
loads. To prevent that, compilers may provide additional functions to
perform unaligned loads/stores, which allow sanitizer instrumentation
to check these accesses too. If the necessary header is available, and
AddressSanitizer is enabled, use them.
* configure.ac: Add check for <sanitizer/common_interface_defs.h>.
* src/lisp.h (UNALIGNED_LOAD_SIZE) [ADDRESS_SANITIZER]: New macro. If
the common sanitizer interface is available and address sanitization
is enabled, define it to __sanitizer_unaligned_load(64|32), depending
on the word size of the architecture.
* src/fns.c [HAVE_FAST_UNALIGNED_ACCESS] (Fstring_lessp): Use
'UNALIGNED_LOAD_SIZE' to perform unaligned loads from the two strings.
Make Emacs build with Xfixes support on old versions of the library
* src/xterm.c (xfixes_toggle_visible_pointer):
(x_toggle_visible_pointer):
(XTtoggle_invisible_pointer, x_term_init): Disable code
requiring fixes 4.0 or later when the fixes library is older.
* src/xterm.h: Define missing types needed by other extensions
when the fixes library is too old.
* configure.ac: Allow building with any version of the Xfixes
extension library.
