Add an option to gen-unicode-ctype.py to read the head and tail of the original i18n file

To avoid having to cut and paste the generated LC_CTYPE character
classes into the new glibc i18n file, read the old file as well. Copy
everything from the old file to the newly generated file except the
LC_CTYPE character class data, which are generated from the
UnicodeData.txt and DerivedCoreProperties.txt given.
Replace accidentally introduced TABS in gen-unicode-ctype.py by spaces