Integrate:

Integrate:
[ 27133]
lastparen in the regexp structure is never initialised, and so will
still be uninitialised after a failed match, yet various points in
mg.c read it come what may. Should fix bug 38461.

[ 27169]
All the bits of clone_params.flags need to be initialised, not just
CLONEf_JOIN_IN.
p4raw-link: @27169 on //depot/perl: 3ae345e35a0fa71a6a704dcc7c7f9ff029895bcd
p4raw-link: @27133 on //depot/perl: 38d1b06f95ebaf0e4dc96d48047c7c7648c3ba3f

p4raw-id: //depot/maint-5.8/perl@27170
p4raw-integrated: from //depot/perl@27168 'merge in'
	ext/threads/threads.xs (@26675..)
p4raw-integrated: from //depot/perl@27133 'merge in' regcomp.c
	(@26764..)