Remove dead typedef macros and harmful u_int*_t redefinitions

The UINT32_TYPE/UINT16_TYPE/INT16_TYPE/UINT8_TYPE/INT8_TYPE/LONGDOUBLE_TYPE
macros (copied from sqlite3.c) were never used anywhere in sqlite-vec.
The u_int8_t/u_int16_t/u_int64_t typedefs redefined standard types using
BSD-only types despite <stdint.h> already being included, breaking builds
on musl/Alpine, strict C99, and requiring reactive platform guards.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>