add (nonstandard) cfmakeraw function

src/termios/cfmakeraw.c

+#include <termios.h>
+
+void cfmakeraw(struct termios *t)
+{
+	t->c_iflag &= ~(IGNBRK|BRKINT|PARMRK|ISTRIP|INLCR|IGNCR|ICRNL|IXON);
+	t->c_oflag &= ~OPOST;
+	t->c_lflag &= ~(ECHO|ECHONL|ICANON|ISIG|IEXTEN);
+	t->c_cflag &= ~(CSIZE|PARENB);
+	t->c_cflag |= CS8;
+	t->c_cc[VMIN] = 1;
+	t->c_cc[VTIME] = 0;
+}