basic columnar-based data structure

[Myrrolinz]

• bit_mask.h: for bitmask
• cypher_string_t.h: A special implementation of string type. The data structure is designed to store a small string or a pointer to a larger string. It consists of a prefix that stores the first few bytes (4 bytes) of the string, followed by a union that can either hold an 8-byte array called data (to store the remaining part of the string) or an 8-byte pointer called overflowPtr. If the total string length fits within the defined SHORT_STR_LENGTH (which is 12 bytes), it can be stored directly within the structure using the prefix and data. If the string is longer, the overflowPtr is used to point to an external memory location that stores the complete string.
• column_vector.h: support int and string vector.

[yannan-wyn]

LGTM