configure.in: -Wno-maybe-uninitialized

* configure.in (warnflags): add -Wno-maybe-uninitialized for gcc
  5, to suppress false warnings in thread.c:do_select().

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@49410 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

configure.in

@@ -791,6 +791,9 @@ if test "$GCC:${warnflags+set}:no" = yes::no; then
     else
 	extra_warning=
     fi
+    if test $gcc_major -eq 5; then
+	extra_warning="$extra_warning -Wno-maybe-uninitialized"
+    fi
     for wflag in -Wno-unused-parameter -Wno-parentheses -Wno-long-long \
 		 -Wno-missing-field-initializers \
 		 -Wunused-variable \