invoke.texi (C++ Dialect Options): Minor copy-edits to x86-specific text.

2012-03-04  Sandra Loosemore  <sandra@codesourcery.com>

	gcc/
	* doc/invoke.texi (C++ Dialect Options): Minor copy-edits to
	x86-specific text.
	(Debugging Options): Likewise.
	(Optimize Options): Likewise.
	(i386 and x86-64 Options): Discuss -march before -mtune, consistently
	with other architectures.  Use official processor names with correct
	spelling/capitalization.  Fix formatting and grammar issues.
	(i386 and x86-64 Windows Options): Similar cleanup here.

From-SVN: r184879