annotate automake snippets with $(AM_V_GEN) and $(AM_V_at)

annotate automake snippets with $(AM_V_GEN) and $(AM_V_at)

This makes it so packages using automake-1.11's silent-rules option
can print e.g., a single "GEN    configmake.h" line, rather than
the 30+ statements that perform the job.  If you want to see the
actual commands, you can still run "make V=1".

Improved-by: Bruno Haible <bruno@clisp.org>
* modules/alloca-opt: Add $(AM_V_GEN) and $(AM_V_at) prefixes
so that make output is abbreviated when those variables are defined
appropriately.
* modules/argz: Likewise.
* modules/arpa_inet: Likewise.
* modules/byteswap: Likewise.
* modules/configmake: Likewise.
* modules/dirent: Likewise.
* modules/errno: Likewise.
* modules/fcntl: Likewise.
* modules/float: Likewise.
* modules/fnmatch: Likewise.
* modules/getopt-posix: Likewise.
* modules/glob: Likewise.
* modules/iconv_open: Likewise.
* modules/inttypes: Likewise.
* modules/localcharset: Likewise.
* modules/locale: Likewise.
* modules/math: Likewise.
* modules/netdb: Likewise.
* modules/netinet_in: Likewise.
* modules/poll: Likewise.
* modules/posix_spawnp-tests: Likewise.
* modules/sched: Likewise.
* modules/search: Likewise.
* modules/selinux-h: Likewise.
* modules/signal: Likewise.
* modules/spawn: Likewise.
* modules/stdarg: Likewise.
* modules/stdbool: Likewise.
* modules/stddef: Likewise.
* modules/stdint: Likewise.
* modules/stdio: Likewise.
* modules/stdlib: Likewise.
* modules/string: Likewise.
* modules/strings: Likewise.
* modules/sys_file: Likewise.
* modules/sys_ioctl: Likewise.
* modules/sys_select: Likewise.
* modules/sys_socket: Likewise.
* modules/sys_stat: Likewise.
* modules/sys_time: Likewise.
* modules/sys_times: Likewise.
* modules/sys_utsname: Likewise.
* modules/sys_wait: Likewise.
* modules/sysexits: Likewise.
* modules/time: Likewise.
* modules/unistd: Likewise.
* modules/wchar: Likewise.
* modules/wctype: Likewise.