libfolly: Update to 2019.06.10.00

Partially restore uclibc patch. Some parts were upstreamed while others
were not.

Fixes compilation without ChaCha20 support in OpenSSL 1.1 and above.

Depend on libunwind conditionally. libunwind is not supported on all
targets. Depending on it unconditionally makes libfolly and dependent
packages unavailable on those targets.

Added missing Maintainer.

Several Makefile rearrangements for consistency.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

libs/libfolly/patches/102-uclibc-patches.patch

@@ -0,0 +1,23 @@
+--- a/folly/CachelinePadded.h
++++ b/folly/CachelinePadded.h
+@@ -35,10 +35,6 @@ namespace folly {
+  */
+ template <typename T>
+ class CachelinePadded {
+-  static_assert(
+-      alignof(T) <= max_align_v,
+-      "CachelinePadded does not support over-aligned types.");
+-
+  public:
+   template <typename... Args>
+   explicit CachelinePadded(Args&&... args)
+--- a/folly/external/farmhash/farmhash.cpp
++++ b/folly/external/farmhash/farmhash.cpp
+@@ -181,6 +181,7 @@
+ 
+ #undef bswap_32
+ #undef bswap_64
++#undef _BYTESWAP_H
+ #include <byteswap.h>
+ 
+ #endif