LibCrypto: Implement the SECP256r1 elliptic curve

This implementation of the secp256r1 elliptic curve uses two techniques
to improve the performance of the operations.

1. All coordinates are stored in Jacobian form, (X/Z^2, Y/Z^3, Z), which
   removes the need for division operations during point addition or
   doubling. The points are converted at the start of the computation,
   and converted back at the end.

2. All values are transformed to Montgomery form, to allow for faster
   modular multiplication using the Montgomery modular multiplication
   method. This means that all coordinates have to be converted into
   this form, and back out of this form before returning them.

Userland/Libraries/LibCrypto/CMakeLists.txt

@@ -17,6 +17,7 @@ set(SOURCES
     Checksum/Adler32.cpp
     Checksum/CRC32.cpp
     Cipher/AES.cpp
+    Curves/SECP256r1.cpp
     Curves/X25519.cpp
     Curves/X448.cpp
     Hash/MD5.cpp