merge revision(s) 66242: [Backport #15387]

	io.c (io_write_nonblock): add RB_GC_GUARD, io_fflush may switch threads

	Since io_fflush may block on mutex or rb_io_wait_readable and
	switch threads, we need to ensure the `str' VALUE returned by
	`rb_obj_as_string` is visible to GC.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_5@66876 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

io.c

@@ -2935,6 +2935,7 @@ io_write_nonblock(VALUE io, VALUE str, VALUE ex)
 
     rb_io_set_nonblock(fptr);
     n = write(fptr->fd, RSTRING_PTR(str), RSTRING_LEN(str));
+    RB_GC_GUARD(str);
 
     if (n == -1) {
 	int e = errno;

version.h

@@ -1,10 +1,10 @@
 #define RUBY_VERSION "2.5.4"
-#define RUBY_RELEASE_DATE "2019-01-17"
-#define RUBY_PATCHLEVEL 131
+#define RUBY_RELEASE_DATE "2019-01-20"
+#define RUBY_PATCHLEVEL 132
 
 #define RUBY_RELEASE_YEAR 2019
 #define RUBY_RELEASE_MONTH 1
-#define RUBY_RELEASE_DAY 17
+#define RUBY_RELEASE_DAY 20
 
 #include "ruby/version.h"