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
diff --git a/libc/Android.mk b/libc/Android.mk
index 417d0ab..72b6dc8 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -125,7 +125,6 @@
 	bionic/sigblock.c \
 	bionic/siginterrupt.c \
 	bionic/siglist.c \
-	bionic/signal.c \
 	bionic/signame.c \
 	bionic/sigsetmask.c \
 	bionic/sleep.c \
@@ -246,6 +245,13 @@
     bionic/seteuid.cpp \
     bionic/setlocale.cpp \
     bionic/signalfd.cpp \
+    bionic/sigaction.cpp \
+    bionic/sigaddset.cpp \
+    bionic/sigdelset.cpp \
+    bionic/sigemptyset.cpp \
+    bionic/sigfillset.cpp \
+    bionic/sigismember.cpp \
+    bionic/signal.cpp \
     bionic/sigpending.cpp \
     bionic/sigprocmask.cpp \
     bionic/sigsuspend.cpp \