partial patch reversla in java/class.c

[Per Bothner <per at bothner dot com>]

I temporaily changed an error to warning in set_constant_value in
java/class.c since otherwise java/util/Calendar.java won't build.
It really should be an error, but something seems corrupted in
the read-in constant pool.  I suspect a garbage collection problem.
If I understand the code, only the constant pool of the "current_jcf"
mark during garbage collection.  We might have multiple active jcf's,
perhaps - I'll ponder the code tomorrow when I'll hopefully be awake.
-- 
	--Per Bothner
per@bothner.com   http://www.bothner.com/per/