Revert part of 2004-04-17 change that moved -frename-registers to -O1.

Revert part of 2004-04-17 change that moved -frename-registers to -O1.

2004-04-19  Paolo Bonzini  <bonzini@gnu.org>

	Revert part of 2004-04-17 change that moved -frename-registers
	to -O1.  -frename-registers is buggy.

	* toplev.c (flag_rename_registers): Initialize to 0.
	* doc/invoke.texi (Optimize options): Move -frename-registers
	to "Not triggered by any -O level" section.  Adjust commentary
	accordingly.

From-SVN: r80887