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>

Removed upstreamed patches. Also fixes a redefinition error on some
platforms.

Cleaned up the DEPENDS to be simpler and more concise.

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

folly is an open-source C++ library developed and used at Facebook.
Adding this package will enable adding further packages that depend on
this.

Depends on PR #7098, PR #7101, PR #7126, PR #7877

Maintainer: me
Compile tested: openwrt-18.06 for ipq40xx, ipq806x, x86 and ar71xx
Run tested: Tested on devices running on the above architectures.
Verified that dependent packages can successfully build and run using
the libfolly.so shared library.

Signed-off-by: Amol Bhave <ambhave@fb.com>