string: Ensure *_chk routines have their hidden builtin definition available

If libc_hidden_builtin_{def,proto} isn't properly set for *_chk routines,
there are unwanted PLT entries in libc.so.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

debug/memcpy_chk.c

@@ -28,3 +28,4 @@ __memcpy_chk (void *dstpp, const void *srcpp, size_t len, size_t dstlen)
 
   return memcpy (dstpp, srcpp, len);
 }
+libc_hidden_builtin_def (__memcpy_chk)

debug/memmove_chk.c

@@ -32,3 +32,4 @@ MEMMOVE_CHK (void *dest, const void *src, size_t len, size_t destlen)
 
   return memmove (dest, src, len);
 }
+libc_hidden_builtin_def (MEMMOVE_CHK)

debug/mempcpy_chk.c

@@ -29,3 +29,4 @@ __mempcpy_chk (void *dstpp, const void *srcpp, size_t len, size_t dstlen)
 
   return __mempcpy (dstpp, srcpp, len);
 }
+libc_hidden_builtin_def (__mempcpy_chk)

debug/memset_chk.c

@@ -26,3 +26,4 @@ __memset_chk (void *dstpp, int c, size_t len, size_t dstlen)
 
   return memset (dstpp, c, len);
 }
+libc_hidden_builtin_def (__memset_chk)

debug/stpcpy_chk.c

@@ -32,3 +32,4 @@ __stpcpy_chk (char *dest, const char *src, size_t destlen)
 
   return memcpy (dest, src, len + 1) + len;
 }
+libc_hidden_builtin_def (__stpcpy_chk)