trivial changes

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@34891 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

range.c

@@ -1037,7 +1037,7 @@ range_alloc(VALUE klass)
  *       end
  *     end
  *
- *  A example of using <code>Xs</code> to construct a range:
+ *  An example of using <code>Xs</code> to construct a range:
  *
  *     r = Xs.new(3)..Xs.new(6)   #=> xxx..xxxxxx
  *     r.to_a                     #=> [xxx, xxxx, xxxxx, xxxxxx]

transcode.c

@@ -2939,7 +2939,7 @@ make_encobj(const char *name)
  *
  * Returns nil if the argument is an ASCII compatible encoding.
  *
- * "corresponding ASCII compatible encoding" is a ASCII compatible encoding which
+ * "corresponding ASCII compatible encoding" is an ASCII compatible encoding which
  * can represents exactly the same characters as the given ASCII incompatible encoding.
  * So, no conversion undefined error occurs when converting between the two encodings.
  *
@@ -3582,7 +3582,7 @@ econv_result_to_symbol(rb_econv_result_t res)
  * primitive_convert converts source_buffer into destination_buffer.
  *
  * source_buffer should be a string or nil.
- * nil means a empty string.
+ * nil means an empty string.
  *
  * destination_buffer should be a string.
  *