Snippets for 9base 6 from Alpine riscv64

Sourced from https://build.alpinelinux.org/buildlogs/build-edge-riscv64/testing/9base/9base-6-r2.log.

• /usr/include/sys/termios.h:1:2: warning: #warning redirecting incorrect #include <sys/termios.h> to <termios.h> [-Wcpp]
      1 | #warning redirecting incorrect #include <sys/termios.h> to <termios.h>
        |  ^~~~~~~
  

• regexp.c:497:39: warning: unsigned conversion from 'int' to 'Rune' {aka 'short unsigned int'} changes value from '1114111' to '65535' [-Woverflow]
    497 |                         classp[n+0] = Runemax;
        |                                       ^~~~~~~