forced to build with standard "gnu17" , ( so, c17 to avoid K&R function declaration problems with slirp, and gnu because there are several classes that use assembly "with the asm" keyword).
Changed socket.c to use socketclose instead of close, and tftpd to use stdio fopen/fseek/fread/fclose instead of posix open/lseek/read/close.
fixed some more warnings
removed chdir and do an absolute path fopen instead.