boost: Fix fiber compilation for mips

The issue was that the pause instruction was emitted through an asm
directive which was not correct for some mips platforms.

Simplified boost-fiber-exclude as a result.

Removed uClibc-ng math patch. It was not correct as it broke float and
long double support (std variants use function overloads). A different
solution was applied upstream. As it's quite annoying to backport, just
wait until a new release comes with that change. ARC as a platform is
barely supported anyways.

Swapped asio patch for the upstream submission, which is unfortunately, in
limbo.

Refreshed remaining patch.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
(cherry-picked from f795779c0a)

libs/boost/patches/002-utime-filesystem.patch

@@ -37,7 +37,7 @@ index 9bba1cf7a..038109d35 100644
  #   include "limits.h"
  
  # else // BOOST_WINDOW_API
-@@ -1451,6 +1453,22 @@ namespace detail
+@@ -1459,6 +1461,22 @@ namespace detail
                          system::error_code* ec)
    {
  #   ifdef BOOST_POSIX_API
@@ -60,7 +60,7 @@ index 9bba1cf7a..038109d35 100644
  
      struct stat path_stat;
      if (error(::stat(p.c_str(), &path_stat)!= 0,
-@@ -1462,6 +1480,8 @@ namespace detail
+@@ -1470,6 +1488,8 @@ namespace detail
      error(::utime(p.c_str(), &buf)!= 0 ? BOOST_ERRNO : 0,
        p, ec, "boost::filesystem::last_write_time");