Ensure PEEK_NEXT_CHAR does not clash with existing variables

https://bugzilla.gnome.org/show_bug.cgi?id=710076
Use unsigned types where appropriate

https://bugzilla.gnome.org/show_bug.cgi?id=710076
Use the right values for checking CRPredefinedAbsoluteFontSize

https://bugzilla.gnome.org/show_bug.cgi?id=710076
gchar/guchar types and casting

https://bugzilla.gnome.org/show_bug.cgi?id=710076
char/xmlChar casting

https://bugzilla.gnome.org/show_bug.cgi?id=710076