sigreturn: print signal mask as a syscall argument
sigreturn: print signal mask as a syscall argument

Although sigreturn takes signal mask via frame pointer,
it's more convenient to display signal mask as a syscall argument
rather than an outstanding object of unknown nature:

Before this change:
    sigreturn() (mask [USR2 CHLD RT_2 RT_3 RT_4 RT_31 RT_32]) = 0

After this change:
    sigreturn({mask=[USR2 CHLD RT_2 RT_3 RT_4 RT_31 RT_32]}) = 0

* signal.c (sys_sigreturn): Display signal mask as a syscall argument.

TeamExodus/external_strace,Distrotech/strace,Distrotech/strace,TeamExodus/external_strace,Infinitive-OS/platform_external_strace,MonkeyZZZZ/platform_external_strace,geofft/strace,cuviper/strace,Yu-AndroidM/android_external_strace,Distrotech/strace,bigzz/strace_android,geofft/strace,MonkeyZZZZ/platform_external_strace,AOSP-YU/platform_external_strace,Infinitive-OS/platform_external_strace,kapdop/android_external_strace,Saruta/strace,YUPlayGodDev/platform_external_strace,bigzz/strace_android,YUPlayGodDev/platform_external_strace,bigzz/strace_android,MonkeyZZZZ/platform_external_strace,vrastogi/strace,AOSP-YU/platform_external_strace,vrastogi/strace,cuviper/strace,AOSP-YU/platform_external_strace,bigzz/strace_android,Yu-AndroidM/android_external_strace,Distrotech/strace,kapdop/android_external_strace,MonkeyZZZZ/platform_external_strace,Yu-AndroidM/android_external_strace,geekboxzone/mmallow_external_strace,vrastogi/strace,geofft/strace,bigzz/strace_android,Saruta/strace,Distrotech/strace,TeamExodus/external_strace,Infinitive-OS/platform_external_strace,geekboxzone/mmallow_external_strace,Yu-AndroidM/android_external_strace,geofft/strace,TeamExodus/external_strace,MonkeyZZZZ/platform_external_strace,Saruta/strace,Yu-AndroidM/android_external_strace,AOSP-YU/platform_external_strace,cuviper/strace,YUPlayGodDev/platform_external_strace,Infinitive-OS/platform_external_strace,vrastogi/strace,YUPlayGodDev/platform_external_strace,Saruta/strace,geekboxzone/mmallow_external_strace,geofft/strace,cuviper/strace,geekboxzone/mmallow_external_strace,TeamExodus/external_strace,Infinitive-OS/platform_external_strace,AOSP-YU/platform_external_strace,Saruta/strace,cuviper/strace,kapdop/android_external_strace,kapdop/android_external_strace,kapdop/android_external_strace,vrastogi/strace,YUPlayGodDev/platform_external_strace,geekboxzone/mmallow_external_strace