[docs] Add mini-"howto" using Qt Creator (osx)
[Qt, OSX] QProgressBar CPU-Issue workaround

fixes #5295
Discourage NOPs reserved for soft-fork upgrades

NOP1 to NOP10 are reserved for future soft-fork upgrades. In the event
of an upgrade such NOPs have *VERIFY behavior, meaning that if their
arguments are not correct the script fails. Discouraging these NOPs by
rejecting transactions containing them from the mempool ensures that
we'll never accept transactions, nor mine blocks, with scripts that are
now invalid according to the majority of hashing power even if we're not
yet upgraded. Previously this wasn't an issue as the IsStandard() rules
didn't allow upgradable NOPs anyway, but 7f3b4e95 relaxed the
IsStandard() rules for P2SH redemptions allowing any redeemScript to be
spent.

We *do* allow upgradable NOPs in scripts so long as they are not
executed. This is harmless as there is no opportunity for the script to
be invalid post-upgrade.
[Qt, OSX] fix usage of osx 10.8+ user notification center

Currently Bitcoin-Qts support for OSX User Notification Center is broken. This pull will fix a known issue of non-official-apple-built apps having problems sending user notifications.
Squashed 'src/secp256k1/' content from commit ad2028f

git-subtree-dir: src/secp256k1
git-subtree-split: ad2028f9890ca40bdd32055aa0fe5c1c9af0e485
Delete src/secp256k1 before subtree import
Merge commit 'd48555b36ac512161b81f9b6bca7bea16a0cd806' as 'src/secp256k1'
Always build and link libsecp256k1
Do not use EC code in global constructors
Use libsecp256k1 in key.cpp
Don't use bashisms in configure
depends: add gmp package
depends: quit exporting in config.site
build: fixup configure to not export anything
build: secp256k1 as a subdir, since it's required
revert part of 9eda1620b

This probably would've broken native OSX builds
Merge pull request #5300

a7f2941 [Qt, OSX] fix usage of osx 10.8+ user notification center (Jonas Schnelli)
Merge pull request #5279

6c8c704 [docs] Add mini-"howto" using Qt Creator (osx) (Jonas Schnelli)
Merge pull request #5220

f9e40fb revert part of 9eda1620b (Cory Fields)
4300876 build: secp256k1 as a subdir, since it's required (Cory Fields)
0dc8613 build: fixup configure to not export anything (Cory Fields)
54566de depends: quit exporting in config.site (Cory Fields)
ff1e5ba depends: add gmp package (Cory Fields)
cf61b54 Don't use bashisms in configure (Pieter Wuille)
dffb8f8 Use libsecp256k1 in key.cpp (Pieter Wuille)
4c97c64 Do not use EC code in global constructors (Pieter Wuille)
07a9901 Always build and link libsecp256k1 (Pieter Wuille)
d48555b Squashed 'src/secp256k1/' content from commit ad2028f (Pieter Wuille)
7a7e109 Delete src/secp256k1 before subtree import (Pieter Wuille)
Remove unused ecwrapper code