Make tests expect [ \t]+ pattern instead of \t for "info reg" command

Make tests expect [ \t]+ pattern instead of \t for "info reg" command

This will allow to format output of "info reg" command as we wish,
without breaking the tests. In particular, it'll let us correctly align
raw and natural values of the registers using spaces instead of current
badly-working approach with tabs.

This change is forwards- and backwards-compatible, so that the amended
tests will work in the same way before and after reformatting patches
(unless the tests check formatting, of course, but I've not come across
any such tests).

Some tests already used this expected pattern, so they didn't
even have to be modified. Others are changed by this patch.

I've checked this on a i386 system, with no noticeable differences in
test results, so at least on i386 nothing seems to be broken by this.

gdb/testsuite/ChangeLog:

	* gdb.arch/powerpc-d128-regs.exp: Replace expected "\[\t\]*" from
	"info reg" with "\[ \t\]*".
	* gdb.arch/altivec-regs.exp: Replace expected "\t" from "info reg" with
	"\[ \t\]+".
	* gdb.arch/s390-multiarch.exp: Ditto.
	* gdb.base/pc-fp.exp: Ditto.
	* gdb.reverse/i386-precsave.exp: Ditto.
	* gdb.reverse/i386-reverse.exp: Ditto.
	* gdb.reverse/i387-env-reverse.exp: Ditto.
	* gdb.reverse/i387-stack-reverse.exp: Ditto.