document like operator

Picodata follow-up

• Follow-up for picodata!1255 (merged)
• See also sbroad!507 (merged)
• Doc pages to change:
  • надо добавить новую страничку в разделе функции и выражения, подобно тому как это сделано для trim/substr
  • совместимость ANSI

Вот полезное описание:

• Support like operator with signature:

expr1 LIKE expr2 [ESCAPE expr3]

which returns TRUE only if expr1 matches the string specified by expr2 (pattern). '_' in pattern matches any single character, '%' matches any character 0 or more times. All other characters match itself according to case.

• Optional escape clause specifies character to use for escaping '_' and '%'

• Default escape character is '\'