Update to latest master to get support for static verification contexts

[sanket1729]

This will greatly simplify the usage of verification contexts for downstream API. We can also use this opportunity to make yet another major release fixing the #370 (Parity mess). I tried naively running the script, but it failed with the following. Maybe someone with more experienced can look at this?

sanket1729@sanket-pc:~/rust-secp256k1/secp256k1-sys$ ./vendor-libsecp.sh depend/ 0_5_0
depend//secp256k1 will be deleted [yn]: y
Cloning into 'secp256k1'...
remote: Enumerating objects: 7439, done.
remote: Counting objects: 100% (222/222), done.
remote: Compressing objects: 100% (106/106), done.
remote: Total 7439 (delta 143), reused 179 (delta 116), pack-reused 7217
Receiving objects: 100% (7439/7439), 8.74 MiB | 768.00 KiB/s, done.
Resolving deltas: 100% (5206/5206), done.
patching file secp256k1/include/secp256k1.h
Hunk #1 succeeded at 218 (offset 16 lines).
Hunk #2 succeeded at 228 (offset 16 lines).
Hunk #3 FAILED at 226.
Hunk #4 succeeded at 321 (offset 16 lines).
Hunk #5 succeeded at 328 (offset 16 lines).
1 out of 5 hunks FAILED -- saving rejects to file secp256k1/include/secp256k1.h.rej
sanket1729@sanket-pc:~/rust-secp256k1/secp256k1-sys$ more depend/secp256k1/include/secp256k1.rej
more: stat of depend/secp256k1/include/secp256k1.rej failed: No such file or directory
sanket1729@sanket-pc:~/rust-secp256k1/secp256k1-sys$ more depend/secp256k1/include/secp256k1.h.rej
*** /dev/null
--- /dev/null
***************
*** 226,228
- SECP256K1_API void secp256k1_context_destroy(
-     secp256k1_context* ctx
- );
--- 0 -----

[sanket1729]

cc @apoelstra . This would really help all projects downstream(including miniscript) because they don't have to carry the verification context around.

[dr-orlovsky]

This issue is closed by the update to the lastest upstream, but I assume the work in removing context where it is not necessary is still pending?

[apoelstra]

Yeah but that's a longer-term issue and out of scope for this issue. Just updating upstream allows the cheap creation of ephemeral contexts which is enough for Sanket's application.