Fixes alignment of xsave area in kernel_fpstate_t. The kernel requires it to be 64-byte aligned. Currently, we aligned the fpstate object itself, instead of the xsave area in it.
Without this, rt_sigreturn and sigreturn crash on x86 32-bit affecting all signal tests. With this fix, many signal tests work again, including linux.signalxxxx, linux.sigplainxxxx, linux.sigcontext, linux.signal_race. linux.alarm, linux.bad-signal-stack, linux.sigsuspend, linux.signest and a few others on Ubuntu 20.04.
Some others (linux.syscall_pwait, client.signal) now show a timeout, and client.events an assert failure. Those fixes will come later.
Issue: #5079, #4953 (closed)