cmake HAVE_DECL_BSWAP_16 examples

Bitcoin-ABC/bitcoin-abc src/config/CMakeLists.txt :51 

check_symbol_exists(bswap_16 "byteswap.h" HAVE_DECL_BSWAP_16)

bitcoin-sv/bitcoin-sv src/config/CMakeLists.txt :62 

check_symbol_exists(bswap_16 "byteswap.h" HAVE_DECL_BSWAP_16)