Fix sigaction(3) for 64-bit.

Also clean up <signal.h> and revert the hacks that were necessary
for 64-bit in linker/debugger.cpp until now.

Change-Id: I3b0554ca8a49ee1c97cda086ce2c1954ebc11892

libc/arch-arm/syscalls.mk

@@ -22,6 +22,7 @@ syscall_src += arch-arm/syscalls/__rt_sigsuspend.S
 syscall_src += arch-arm/syscalls/__rt_sigtimedwait.S
 syscall_src += arch-arm/syscalls/__sched_getaffinity.S
 syscall_src += arch-arm/syscalls/__set_tls.S
+syscall_src += arch-arm/syscalls/__sigaction.S
 syscall_src += arch-arm/syscalls/__statfs64.S
 syscall_src += arch-arm/syscalls/__sys_clone.S
 syscall_src += arch-arm/syscalls/__syslog.S
@@ -178,7 +179,6 @@ syscall_src += arch-arm/syscalls/settimeofday.S
 syscall_src += arch-arm/syscalls/setuid.S
 syscall_src += arch-arm/syscalls/setxattr.S
 syscall_src += arch-arm/syscalls/shutdown.S
-syscall_src += arch-arm/syscalls/sigaction.S
 syscall_src += arch-arm/syscalls/sigaltstack.S
 syscall_src += arch-arm/syscalls/signalfd4.S
 syscall_src += arch-arm/syscalls/socket.S

libc/arch-arm/syscalls/__sigaction.S

@@ -4,7 +4,7 @@
 #include <linux/err.h>
 #include <machine/asm.h>
 
-ENTRY(sigaction)
+ENTRY(__sigaction)
     mov     ip, r7
     ldr     r7, =__NR_sigaction
     swi     #0
@@ -13,4 +13,4 @@ ENTRY(sigaction)
     bxls    lr
     neg     r0, r0
     b       __set_errno
-END(sigaction)
+END(__sigaction)