added support for reduced font bitmaps with lower case characters

added support for reduced font bitmaps with lower case characters

While support for font bitmaps with full ISO-8859-1 character maps
already exists, this change adds support for specially crafted font
bitmaps containing the usual reduced character map plus lower case
characters (including umlaut characters) by choosing ".frames: 112"
for the font definition. To use this, the last line in the font's
character map that looks like this

©ÄÖÜ°™_

is replaced with the following three lines (where the underscore
characters are usually replaced with filled, cursor style blocks):

`abcdefghijklmno
pqrstuvwxyz{|}~_
©ÄÖÜ°™_äöüß

The layout of the characters in the font bitmap may differ from the
above example (which reflects the default font bitmap layout), and can
be set using the ".frames_per_line" configuration option (which would
be "16" for the example above).

(In fact, this extended, reduced font character map currently has only
107 characters defined, so a few special characters may be added later
to the remaining five slots.)