Fix documentation typos

Character entities are not supposed to be supported by gtk-doc¹ and
fix the spelling of ‘optional’

¹https://bugzilla.gnome.org/show_bug.cgi?id=758137

https://bugzilla.gnome.org/show_bug.cgi?id=758174

glib/gconvert.c

@@ -79,13 +79,13 @@
  * "Presentación.sxi". If the application which created it uses
  * ISO-8859-1 for its encoding,
  * |[
- * Character:  P  r  e  s  e  n  t  a  c  i  ó  n  .  s  x  i
+ * Character:  P  r  e  s  e  n  t  a  c  i  ó  n  .  s  x  i
  * Hex code:   50 72 65 73 65 6e 74 61 63 69 f3 6e 2e 73 78 69
  * ]|
  * However, if the application use UTF-8, the actual file name on
  * disk would look like this:
  * |[
- * Character:  P  r  e  s  e  n  t  a  c  i  ó     n  .  s  x  i
+ * Character:  P  r  e  s  e  n  t  a  c  i  ó     n  .  s  x  i
  * Hex code:   50 72 65 73 65 6e 74 61 63 69 c3 b3 6e 2e 73 78 69
  * ]|
  * Glib uses UTF-8 for its strings, and GUI toolkits like GTK+ that use
@@ -986,7 +986,7 @@ filename_charset_cache_free (gpointer data)
  * and said environment variables have no effect.
  *
  * `G_FILENAME_ENCODING` may be set to a comma-separated list of
- * character set names. The special token "@locale" is taken
+ * character set names. The special token "\@locale" is taken
  * to  mean the character set for the [current locale][setlocale].
  * If `G_FILENAME_ENCODING` is not set, but `G_BROKEN_FILENAMES` is,
  * the character set of the current locale is taken as the filename

glib/giochannel.c

@@ -103,7 +103,7 @@
  *            various functions such as g_io_channel_write_chars() to
  *            write raw bytes to the channel.  Encoding and buffering
  *            issues are dealt with at a higher level.
- * @io_seek: (optional) seeks the channel.  This is called from
+ * @io_seek: (optional) seeks the channel.  This is called from
  *           g_io_channel_seek() on channels that support it.
  * @io_close: closes the channel.  This is called from
  *            g_io_channel_close() after flushing the buffers.

glib/gregex.c

@@ -64,7 +64,7 @@
  * Note that, unless you set the #G_REGEX_RAW flag, all the strings passed
  * to these functions must be encoded in UTF-8. The lengths and the positions
  * inside the strings are in bytes and not in characters, so, for instance,
- * "\xc3\xa0" (i.e. "à") is two bytes long but it is treated as a
+ * "\xc3\xa0" (i.e. "à") is two bytes long but it is treated as a
  * single character. If you set #G_REGEX_RAW the strings can be non-valid
  * UTF-8 strings and a byte is treated as a character, so "\xc3\xa0" is two
  * bytes and two characters long.

glib/gregex.h

@@ -56,7 +56,7 @@ G_BEGIN_DECLS
  *     Since 2.16
  * @G_REGEX_ERROR_NOTHING_TO_REPEAT: Nothing to repeat. Since 2.16
  * @G_REGEX_ERROR_UNRECOGNIZED_CHARACTER: Unrecognized character after "(?",
- *     "(?<" or "(?P". Since 2.16
+ *     "(?<" or "(?P". Since 2.16
  * @G_REGEX_ERROR_POSIX_NAMED_CLASS_OUTSIDE_CLASS: POSIX named classes are
  *     supported only within a class. Since 2.16
  * @G_REGEX_ERROR_UNMATCHED_PARENTHESIS: Missing terminating ")" or ")"

glib/gstrfuncs.c

@@ -2119,7 +2119,7 @@ out:
  * @exceptions: (nullable): a string of characters not to escape in @source
  *
  * Escapes the special characters '\b', '\f', '\n', '\r', '\t', '\v', '\'
- * and '"' in the string @source by inserting a '\' before
+ * and '"' in the string @source by inserting a '\' before
  * them. Additionally all characters in the range 0x01-0x1F (everything
  * below SPACE) and in the range 0x7F-0xFF (all non-ASCII chars) are
  * replaced with a '\' followed by their octal representation.

gobject/gvaluearray.c

@@ -257,7 +257,7 @@ g_value_array_append (GValueArray  *value_array,
 /**
  * g_value_array_insert:
  * @value_array: #GValueArray to add an element to
- * @index_: insertion position, must be <= value_array-&gt;n_values
+ * @index_: insertion position, must be <= value_array->;n_values
  * @value: (allow-none): #GValue to copy into #GValueArray, or %NULL
  *
  * Insert a copy of @value at specified position into @value_array. If @value