Fix error handling when parsing XML via IO.pipe (#221)

## Why?

If via IO.pipe, `IOError` exception is not raised, but `Errno::ESPIPE`
or `Errno::EPIPE` or `Errno::EINVAL` exception is raised.

- CRuby
```
@er_source.pos
#=> Errno::ESPIPE Exception: Illegal seek
```

- CRuby (Windows (Ruby 2.6 or earlier))
```
@er_source.pos
#=> Errno::EINVAL: Invalid argument
```

- JRuby
```
@er_source.pos
#=> Errno::EPIPE: Broken pipe - No message available
```

Co-authored-by: Sutou Kouhei <kou@clear-code.com>

lib/rexml/source.rb

@@ -321,7 +321,7 @@ def current_line
         rescue
         end
         @er_source.seek(pos)
-      rescue IOError
+      rescue IOError, SystemCallError
         pos = -1
         line = -1
       end

test/parse/test_text.rb

@@ -6,10 +6,7 @@ class TestParseText < Test::Unit::TestCase
     class TestInvalid < self
       def test_text_only
         exception = assert_raise(REXML::ParseException) do
-          parser = REXML::Parsers::BaseParser.new('a')
-          while parser.has_next?
-            parser.pull
-          end
+          REXML::Parsers::BaseParser.new('a').pull
         end
 
         assert_equal(<<~DETAIL.chomp, exception.to_s)
@@ -21,6 +18,25 @@ def test_text_only
         DETAIL
       end
 
+      def test_text_only_with_io_pipe
+        IO.pipe do |reader, writer|
+          writer.write('a')
+          writer.close
+
+          exception = assert_raise(REXML::ParseException) do
+            REXML::Parsers::BaseParser.new(reader).pull
+          end
+
+          assert_equal(<<~DETAIL.chomp, exception.to_s)
+            Malformed XML: Content at the start of the document (got 'a')
+            Line: -1
+            Position: -1
+            Last 80 unconsumed characters:
+
+          DETAIL
+        end
+      end
+
       def test_before_root
         exception = assert_raise(REXML::ParseException) do
           parser = REXML::Parsers::BaseParser.new('b<a></a>')