fn() isalnum

Check if character is alphanumeric.

/*!
 * @fn isalnum
 * 
 * @headerfile <cctype>
 * 
 * @brief Check if character is alphanumeric.
 * 
 * @signature bool isalnum(c);
 * 
 * @param[in] c The character to be checked. Type: <tt>int</tt>
 * 
 * @return bool <tt>true</tt> (non-zero) if <tt>c</tt> is alphanumeric.
 * 
 * @section Remarks
 * 
 * This is non-SeqAn, plain c and listed for completeness.
 * 
 * @see http://www.cplusplus.com/reference/clibrary/cctype/isalnum/
 * @see http://www.cppreference.com/wiki/string/character_classes
 * @see FileFormatTokenization#readAlphaNums
 * @see FileFormatTokenization#readIdentifier
 */