Remove four libcxx known failures now that mkstemp/get_temp_file_name works.

pnacl/scripts/libcxx_known_failures.txt

 # Newlib is missing <fenv.h>, which is currently very platform-specific.
 libc++::depr/depr.c.headers/fenv_h.pass.cpp
 libc++::numerics/cfenv/cfenv.syn/cfenv.pass.cpp
 libc++::numerics/cfenv/version.pass.cpp
 
 # Newlib doesn't have support for long double in <math.h>. <cmath> was
 # modified to work around these issues. Discuss fixing the test with
 # libc++ folks?
 libc++::depr/depr.c.headers/math_h.pass.cpp
 libc++::numerics/c.math/cmath.pass.cpp
 
 # The test is run without __STRICT_ANSI__ (-std=gnu++11 instead of
 # -std=c++11) which makes us define what shouldn't be defined in
 # clang/3.3/include/stdbool.h.
 libc++::depr/depr.c.headers/stdbool_h.pass.cpp
 
 # Newlib doesn't have the C Unicode TR header <uchar.h>.
 libc++::depr/depr.c.headers/uchar_h.pass.cpp
 
 # Newlib defines clearerr, feof and ferror as macro which shadows the
 # functions it also declares. <cstdio> was patched to undef the macros,
 # but the test includes <stdio.h> instead. Discuss fixing the test with
 # libc++ folks?
 libc++::depr/depr.c.headers/stdio_h.pass.cpp
 
 # Need to investigate these.
 libc++::diagnostics/syserr/syserr.errcat/syserr.errcat.objects/system_category.pass.cpp
-libc++::input.output/file.streams/fstreams/fstream.assign/member_swap.pass.cpp
-libc++::input.output/file.streams/fstreams/fstream.assign/nonmember_swap.pass.cpp
-libc++::input.output/file.streams/fstreams/ofstream.assign/member_swap.pass.cpp
-libc++::input.output/file.streams/fstreams/ofstream.assign/nonmember_swap.pass.cpp
 libc++::localization/locale.categories/category.numeric/locale.nm.put/facet.num.put.members/put_long_double.pass.cpp
 libc++::localization/locale.categories/category.time/locale.time.put/locale.time.put.members/put2.pass.cpp
 libc++::re/re.traits/isctype.pass.cpp
 libc++::re/re.traits/lookup_classname.pass.cpp
 libc++::strings/string.conversions/stod.pass.cpp
 libc++::strings/string.conversions/stof.pass.cpp
 libc++::strings/string.conversions/stold.pass.cpp
 
 # terminating with uncaught exception of type std::runtime_error:
 # <some class> failed to construct for <some locale like en_US.UTF-8>
@@ skipping 47 matching lines @@
 libc++::localization/locales/locale/locale.statics/classic.pass.cpp
 libc++::localization/locales/locale/locale.statics/global.pass.cpp
 libc++::re/re.regex/re.regex.locale/imbue.pass.cpp
 libc++::re/re.traits/default.pass.cpp
 libc++::re/re.traits/getloc.pass.cpp
 libc++::re/re.traits/imbue.pass.cpp
 libc++::re/re.traits/translate_nocase.pass.cpp
 
 # This relies on sigaction to capture SIGALRM.
 libc++::thread/thread.threads/thread.thread.this/sleep_for.pass.cpp