[Cin] Compile on Arch Linux

[Andrea paz]

I compiled CinGG after formatting and installing arch linux, so on a
pretty clean environment. The compile failed due to lack of "ctags"
and "libwebp". Moreover, as already mentioned, for arch linux package
"libtoolize" is called "libtool" and "libaom" is called "aom". Perhaps
it is better to update "README.arch" in the download page:

https://cinelerra-gg.org/download/pkgs/README.arch

My curiosity:

I noticed these Warnings in cin5.log; are they important?

makeinfo --html --no-split cinelerra.texi
cinelerra.texi:12: warning: missing argument for @center
cinelerra.texi:8791: warning: The nodes next «PLUGIN GUI'S WHICH
UPDATE DURING PLAYBACK» on menù «USING OPENGL» and in the sectioning
«PLUGIN QUERIES» are different
cinelerra.texi:8834: warning: the node «USING OPENGL» is next for
«PLUGIN QUERIES» in the sectioning, but not in the menu
cinelerra.texi:8834: warning: the nodes prev «PLUGIN QUERIES» in the
menu «USING OPENGL» and in the sectioning «PLUGIN GUI'S WHICH UPDATE
DURING PLAYBACK» are different
cinelerra.texi:8992: warning: the node «PLUGIN QUERIES» is next for
«USING OPENGL» in the menu, but not in the sectioning
cinelerra.texi:8992: warning: the nodes prev «USING OPENGL» in the
menu «PLUGIN GUI'S WHICH UPDATE DURING PLAYBACK» and in the sectioning
«PLUGIN QUERIES» are different
make[2]: exit from the directory "/home/paz/cinelerra5/cinelerra-5.1/doc"