Some locale settings let make fail or create wrong results
because tr '[:lower:]' '[:upper:]' which is used to convert
from lower to upper case depends on the locale.

With locale tr_TR.UTF-8, lower case 'i' is not converted to 'I'.
This results in wrong entries in config-host.h like these ones:

  #define CONFIG_QEMU_PREFiX "/usr/local"
  #define CONFIG_QEMU_BiNDiR "/usr/local/bin"

This problem was reported by Emre Ersin.

The same problem occurs when configure creates the target specific
files config-target.mak. They get wrong declarations:

TARGET_CRiS=y
TARGET_i386=y
TARGET_MiCROBLAZE=y
TARGET_MiPS64=y
TARGET_MiPS=y
TARGET_UNiCORE32=y

It is sufficient to restrict the conversion to the characters a-z.

Using this explicit range avoids the dependency on the locale
settings and is also shorter.

v2:
POSIX says that 'tr a-z' is unspecified outside of the POSIX
locale, so we must set LC_ALL=C to make sure that we are using
POSIX (hint from Eric Blake, thanks).

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>