Hotfix 7.0.1 release required

[Reini Urban]

I just detected and fixed two serious and two minor bugs which would
require a 7.0.1 release:

- GC regression --optimize caused by PARROT_CANNOT_RETURN_NULL #1186
https://github.com/parrot/parrot/issues/1186

This causes segfaults with --optimize, which is the default for nqp
and rakudo, on better (i.e. newer) compilers. The bug was there since
3.6, but turned evil only with 7.0, when packfile refactored.

- threads deadlock in gc_gms_mark_and_sweep() #1187
https://github.com/parrot/parrot/issues/1187

With cc -O3 the lock code is too far away from the guard, thus causing
our threads example examples/threads/chameneos.pbc to hang, a
regression from 6.11.0

And 2 minor ones for --m=64 or --m=32:

- fix --m=64 with gcc on ppc64 and mips64 #1181

--m=64 produced wrong ld and linkflags since 6.10, GH #1110

- fix icu probes with --m #1182

We never linked icu again the libs in the configure step, so we failed
to detect wrong architectures, and worse, added wrong arch include and
libpaths to the flags (e.g. amd64 --m=32), causing all sorts of icu
errors, when has_icu=1 but either linking or runtime failed. This
always caused problems.

I made two more fixes in the meantime:

- Optimize ExtUtils::Command away on posix systems #1177

- x86_86: missing parrot_i386_cmpxchg #1173

which probably shouldn't make it into 7.0.1

branch: smoke-me/7.0.1
-- 
Reini Urban
http://cpanel.net/   http://www.perl-compiler.org/