* fsusage.m4 (gl_STATFS_TRUNCATES): Avoid unused variable. * getdate.m4 (gl_C_COMPOUND_LITERALS): Likewise. * jm-winsz1.m4 (gl_HEADER_TIOCGWINSZ_IN_TERMIOS_H): Likewise; also add missing comma that caused broken test. * link-follow.m4 (gl_AC_FUNC_LINK_FOLLOWS_SYMLINK): Include stdlib.h, for `abort'. * ls-mntd-fs.m4 (gl_LIST_MOUNTED_FILE_SYSTEMS): Avoid unused variables. * mkdir-slash.m4 (gl_FUNC_MKDIR_TRAILING_SLASH): Check for and include unistd.h if present, for `rmdir'. * physmem.m4 (gl_SYS__SYSTEM_CONFIGURATION): Avoid unused variables. * putenv.m4 (gl_FUNC_PUTENV): Rewrite using AC_RUN_IFELSE, and in the process include standard headers for prototypes. * readutmp.m4 (gl_READUTMP): Require AC_GNU_SOURCE, so utmpxname gets declared on GNU/Linux. * rmdir-errno.m4 (gl_FUNC_RMDIR_NOTEMPTY): Check for and include unistd.h, for `rmdir'. * time_r.m4 (gl_TIME_R): Avoid unused variables.