Merge current secp256k1 subtree

[maflcko]

The subtree should now match upstream again. Check with:

./contrib/devtools/git-subtree-check.sh src/secp256k1

The changes are only documentation/refactoring related.

[sipa]

utACK 999968e

$ ./contrib/devtools/git-subtree-check.sh src/secp256k1
src/secp256k1 in HEAD was last updated to upstream commit 0b7024185045a49a1a6a4c5615bf31c94f63d9c4 (tree af619602c243e0d8fbd5934f375faa4aedb4ca6e)
src/secp256k1 in HEAD currently refers to tree af619602c243e0d8fbd5934f375faa4aedb4ca6e
GOOD

[fanquake]

utACK 999968e

[pull/11421/local-merge ec741b135] Merge #11421: Merge current secp256k1 subtree
 Date: Mon Oct 2 15:13:09 2017 +0800
#11421 Merge current secp256k1 subtree into master
* 999968e41 Bump secp256k1 subtree (MarcoFalke) (pull/11421/head)
* fd86f998f Squashed 'src/secp256k1/' changes from 84973d393..0b7024185 (MarcoFalke)

Dropping you on a shell so you can try building/testing the merged source.
Run 'git diff HEAD~' to show the changes being merged.
Type 'exit' when done.
bash-3.2$ git fetch https://github.com/bitcoin-core/secp256k1.git
warning: no common commits
remote: Counting objects: 4040, done.
remote: Compressing objects: 100% (5/5), done.
remote: Total 4040 (delta 1), reused 5 (delta 1), pack-reused 4034
Receiving objects: 100% (4040/4040), 1.61 MiB | 98.00 KiB/s, done.
Resolving deltas: 100% (2837/2837), done.
From https://github.com/bitcoin-core/secp256k1
 * branch                HEAD       -> FETCH_HEAD
bash-3.2$ contrib/devtools/git-subtree-check.sh src/secp256k1
src/secp256k1 in HEAD was last updated to upstream commit 0b7024185045a49a1a6a4c5615bf31c94f63d9c4 (tree af619602c243e0d8fbd5934f375faa4aedb4ca6e)
src/secp256k1 in HEAD currently refers to tree af619602c243e0d8fbd5934f375faa4aedb4ca6e
GOOD

Compiled and ran through a make check as well.

PASS: qt/test/test_bitcoin-qt
/Applications/Xcode.app/Contents/Developer/usr/bin/make  check-TESTS
PASS: exhaustive_tests
PASS: tests
============================================================================
Testsuite summary for libsecp256k1 0.1
============================================================================
# TOTAL: 2
# PASS:  2
# SKIP:  0
# XFAIL: 0
# FAIL:  0
# XPASS: 0
# ERROR: 0
============================================================================
  CXX      test/test_unitester-unitester.o
  CXXLD    test/unitester
/Applications/Xcode.app/Contents/Developer/usr/bin/make  check-TESTS
PASS: test/unitester
============================================================================
Testsuite summary for univalue 1.0.2
============================================================================
# TOTAL: 1
# PASS:  1
# SKIP:  0
# XFAIL: 0
# FAIL:  0
# XPASS: 0
# ERROR: 0
============================================================================
PASS: test/test_bitcoin
============================================================================
Testsuite summary for Bitcoin Core 0.15.99
============================================================================
# TOTAL: 2
# PASS:  2
# SKIP:  0
# XFAIL: 0
# FAIL:  0
# XPASS: 0
# ERROR: 0
============================================================================
Making check in doc/man
make[1]: Nothing to be done for `check'.
make[1]: Nothing to be done for `check-am'.