Remove files imported via autogen.sh.

* m4/.gitignore: Ignore these files.
* m4/codeset.m4: Remove file.
* m4/gettext.m4: Likewise.
* m4/glibc2.m4: Likewise.
* m4/glibc21.m4: Likewise.
* m4/iconv.m4: Likewise.
* m4/intdiv0.m4: Likewise.
* m4/intl.m4: Likewise.
* m4/intldir.m4: Likewise.
* m4/intlmacosx.m4: Likewise.
* m4/intltool.m4: Likewise.
* m4/inttypes-pri.m4: Likewise.
* m4/inttypes.m4: Likewise.
* m4/inttypes_h.m4: Likewise.
* m4/isc-posix.m4: Likewise.
* m4/lcmessage.m4: Likewise.
* m4/lib-ld.m4: Likewise.
* m4/lib-link.m4: Likewise.
* m4/lib-prefix.m4: Likewise.
* m4/lock.m4: Likewise.
* m4/longdouble.m4: Likewise.
* m4/longlong.m4: Likewise.
* m4/nls.m4: Likewise.
* m4/po.m4: Likewise.
* m4/printf-posix.m4: Likewise.
* m4/progtest.m4: Likewise.
* m4/signed.m4: Likewise.
* m4/size_max.m4: Likewise.
* m4/stdint_h.m4: Likewise.
* m4/uintmax_t.m4: Likewise.
* m4/ulonglong.m4: Likewise.
* m4/visibility.m4: Likewise.
* m4/wchar_t.m4: Likewise.
* m4/wint_t.m4: Likewise.
* m4/xsize.m4: Likewise.