elf: Ignore loader debug env vars for setuid

Loader already ignores LD_DEBUG, LD_DEBUG_OUTPUT, and
LD_TRACE_LOADED_OBJECTS. Both LD_WARN and LD_VERBOSE are similar to
LD_DEBUG, in the sense they enable additional checks and debug
information, so it makes sense to disable them.

Also add both LD_VERBOSE and LD_WARN on filtered environment variables
for setuid binaries.

Checked on x86_64-linux-gnu.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

sysdeps/generic/unsecvars.h

@@ -16,6 +16,8 @@
   "LD_PRELOAD\0"							      \
   "LD_PROFILE\0"							      \
   "LD_SHOW_AUXV\0"							      \
+  "LD_VERBOSE\0"							      \
+  "LD_WARN\0"								      \
   "LOCALDOMAIN\0"							      \
   "LOCPATH\0"								      \
   "MALLOC_ARENA_MAX\0"							      \