utf8.h: Remove some EBCDIC dependencies

utf8.h: Remove some EBCDIC dependencies

regen/regcharclass.pl has been enhanced in previous commits so that it
generates as good code as these hand-defined macro definitions for
various UTF-8 constructs.  And, it should be able to generate EBCDIC
ones as well.  By using its definitions, we can remove the EBCDIC
dependencies for them.  It is quite possible that the EBCDIC versions
were wrong, since they have never been tested.  Even if
regcharclass.pl has bugs under EBCDIC, it is easier to find and fix
those in one place, than all the sundry definitions.