v3.1.5

• Add appveyor.com config
• Change arg value from int to const uint16_t in modbus_write_register
• Mark raw_req argument as const in modbus_send_raw_request (closes #479)
• Add unit tests for VD-1301 and VD-1302 vulnerabilities
• Fix VD-1301 and VD-1302 vulnerabilities
• Create CODE_OF_CONDUCT.md
• modbus_mapping_t is now a named typedef (to allow forward declaration)
• Rename type as flags for consistency between functions
• Add missing SOCK_CLOEXEC flag on socket creation
• Remove wrong and harmful checks in configure.ac
• Oops fix OR on RS485 settings (1c5d969)
• Only set SER_RS485_ENABLED bit of existing RS485 settings
• Add .vscode/ to .gitignore
• Fix wrong function name
• Remove a duplicated semi-colon
• Fix a small typo in test message
• Fix modbus_reply for TCP when unit id == 0 (fixes #376)
• New functions to define the indication timeout (#95)
• Remove CYGWIN condition to provide bswap16 fallback (#383)
• Use builtin bswap16 of gcc 4.8 (#377)
• Handle out-of-memory conditions more gracefully
• Add entry points for accept/listen in libmodbus index
• Refine issue template for Github
• Move WINVER definition before other includes (#350)
• Add new function modbus_get_slave()
• Fix LIBMODBUS_VERSION_HEX encoding (closes #345)
• tcp_modbus_accept mustn't close socket on error (closes #333)