Generation of locales: made call to tr more robust and added LOWERCASE macro

When calling 'tr' without quoting braces, bash can make really weird things
if there are existing 'single-letter-named' directories
eg:
thierry@thierry-desktop:~$ echo AAA | tr [A-Z] [a-z]
aaa
thierry@thierry-desktop:~$ mkdir m
thierry@thierry-desktop:~$ echo AAA | tr [A-Z] [a-z]
AAA

The (quick) analysis is that the callee (tr) argvs then
contain 'm' thus the translation does not work

Using quotes works around it:
thierry@thierry-desktop:~$ echo AAA | tr '[A-Z]' '[a-z]'
aaa

Signed-off-by: Thierry Bultel <thierry.bultel@wanadoo.fr>
Reviewed-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>