String functions

Most case-insensitive string functions use toupper and tolower, which don't support non-ASCII characters.

• bool StrIsEmpty(str s) – returns true if S is an empty string (“”). Do not use with invalid string ids.
• bool StrEquals(str a, str b) – returns true if strings are equal. Wrapper for StrCmp.
• bool StrIEquals(str a, str b) returns true if strings are equal (case-insensitive). Wrapper for StrICmp.