ruvm 0.5.2

This patch is mostly M6, with the first sound cards and two local display windows, plus signal delivery for M7.

For M6: AC97 is in with -device AC97 and -audio model=ac97 (#201), and so is Intel HD Audio as intel-hda and ich9-intel-hda with the hda-duplex, hda-output and hda-micro codecs and -audio model=hda (#204). A small guest that drives the HDA controller and plays a fixed PCM gives the same serial output and a byte for byte identical wav file under ruvm and QEMU 11.1, across 19 setups covering every codec, five stream formats, resampling, ich9 and MSI. 8 bit streams are left out of that check because QEMU's own output changes from run to run there. The audio backends now run on the machine's virtual clock and stop with the VM. -display sdl is in behind the ui-sdl cargo feature (#202), and -display gtk on GTK 4 behind ui-gtk (#205). Under Xvfb the window shows the same pixels as a QMP screendump, the captions and window sizes follow QEMU's, and keys, pointer moves, clicks, the wheel and the hotkeys reach the guest as the same bytes QEMU gives it. GTK 4 can't grab or warp the pointer, and there is no GL, VTE console or clipboard yet.

For M7: qemu-x86_64 now delivers signals the way QEMU's linux-user does (#203), with the kernel's rt_sigframe and the FXSAVE or XSAVE image, rt_sigreturn, sigaltstack, signalfd, the rt_sig* calls, and QEMU's safe_syscall so a signal that arrives right before a blocking call is never slept through. CPU faults turn into SIGSEGV, SIGBUS, SIGFPE, SIGILL and SIGTRAP with QEMU's si_code and address. Threads and the /proc emulation are next.

What's Changed

• hw-audio: AC97 with -device AC97 and -audio model=ac97 by @tamnd in #201
• ui: -display sdl behind the ui-sdl feature by @tamnd in #202
• linux-user: signal delivery for x86_64 guests by @tamnd in #203
• audio: Intel HD Audio and the hda codecs by @tamnd in #204
• ui: -display gtk behind the ui-gtk feature by @tamnd in #205
• Release 0.5.2 by @tamnd in #206

Full Changelog: v0.5.1...v0.5.2