Add stpcpy/stpncpy.

Add tests for the above.

Add the fortify implementations of __stpcpy_chk and __stpncpy_chk.

Modify the strncpy test to cover more cases and use this template for
stpncpy.

Add all of the fortify test cases.

Bug: 13746695
Change-Id: I8c0f0d4991a878b8e8734fff12c8b73b07fdd344
diff --git a/libc/private/libc_events.h b/libc/private/libc_events.h
index 5d20f4b..f2b973d 100644
--- a/libc/private/libc_events.h
+++ b/libc/private/libc_events.h
@@ -40,6 +40,8 @@
 #define BIONIC_EVENT_STRNCPY_BUFFER_OVERFLOW  80120
 #define BIONIC_EVENT_MEMSET_BUFFER_OVERFLOW   80125
 #define BIONIC_EVENT_STRCPY_BUFFER_OVERFLOW   80130
+#define BIONIC_EVENT_STPCPY_BUFFER_OVERFLOW   80135
+#define BIONIC_EVENT_STPNCPY_BUFFER_OVERFLOW  80140
 
 #define BIONIC_EVENT_RESOLVER_OLD_RESPONSE    80300
 #define BIONIC_EVENT_RESOLVER_WRONG_SERVER    80305