tcg: Move some opcode generation functions out of line

Some of these functions are really quite large.  We have a number of
things that ought to be circularly dependent, but we duplicated code
to break that chain for the inlines.

This saved 25% of the code size of one of the translators I examined.

Reviewed-by: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Signed-off-by: Richard Henderson <rth@twiddle.net>