doc: Reorder list of programming languages.
* gettext-tools/doc/lang-c.texi: New file, extracted from
gettext-tools/doc/gettext.texi.
* gettext-tools/doc/lang-python.texi: Likewise.
* gettext-tools/doc/lang-java.texi: Likewise.
* gettext-tools/doc/lang-csharp.texi: Likewise.
* gettext-tools/doc/lang-javascript.texi: Likewise.
* gettext-tools/doc/lang-scheme.texi: Likewise.
* gettext-tools/doc/lang-lisp.texi: Likewise.
* gettext-tools/doc/lang-clisp-c.texi: Likewise.
* gettext-tools/doc/lang-elisp.texi: Likewise.
* gettext-tools/doc/lang-librep.texi: Likewise.
* gettext-tools/doc/lang-ruby.texi: Likewise.
* gettext-tools/doc/lang-sh.texi: Likewise.
* gettext-tools/doc/lang-bash.texi: Likewise.
* gettext-tools/doc/lang-gawk.texi: Likewise.
* gettext-tools/doc/lang-lua.texi: Likewise.
* gettext-tools/doc/lang-pascal.texi: Likewise.
* gettext-tools/doc/lang-smalltalk.texi: Likewise.
* gettext-tools/doc/lang-vala.texi: Likewise.
* gettext-tools/doc/lang-wxwidgets.texi: Likewise.
* gettext-tools/doc/lang-tcl.texi: Likewise.
* gettext-tools/doc/lang-perl.texi: Likewise.
* gettext-tools/doc/lang-php.texi: Likewise.
* gettext-tools/doc/lang-pike.texi: Likewise.
* gettext-tools/doc/lang-gcc-source.texi: Likewise.
* gettext-tools/doc/lang-ycp.texi: Likewise.
* gettext-tools/doc/Makefile.am (gettext_TEXINFOS): Add them.
* gettext-tools/doc/gettext.texi (List of Programming Languages): Reorder list
of programming languages, approximately according to decreasing importance.
(PO Files): Reorder list for format string markers accordingly.
(Translators for other Languages): Likewise.
