Add MacPorts default include/lib paths for OSX
add pkg-config support
packaging: remove the --with-pkgconfigdir option

It was not necessary and would only confuse packagers.
packaging: fixup pkg-config

Set the private libs as determined by configure, and add the missing lib link.
packaging: add pkg-config file to gitignore
secp256k1_fe_sqrt checks for success

- secp256k1_fe_sqrt now checks that the value it calculated is actually a square root.
- Add return values to secp256k1_fe_sqrt and secp256k1_ge_set_xo.
- Callers of secp256k1_ge_set_xo can use return value instead of explicit validity checks
- Add random value tests for secp256k1_fe_sqrt
Use endomorphism in precomputations
Documented autotools build process in readme
Support 64bit_asm field on OSX
Merge pull request #23

17eec03 Support 64bit_asm field on OSX (Peter Dettman)
Merge pull request #22

7fc1fb4 Documented autotools build process in readme (John Driscoll)
Merge pull request #20

d7fd4d0 Use endomorphism in precomputations (Peter Dettman)
Merge pull request #19

09ca4f3 secp256k1_fe_sqrt checks for success (Peter Dettman)
Merge pull request #17

a86f241 Add MacPorts default include/lib paths for OSX (Peter Dettman)
A few improvements to the sqrt tests
Rewrite 5x52 normalize method to be faster
Merge pull request #18

4212f7d packaging: add pkg-config file to gitignore (Cory Fields)
67a4765 packaging: fixup pkg-config (Cory Fields)
81b2fae packaging: remove the --with-pkgconfigdir option (Cory Fields)
c7ee71f add pkg-config support (Amir Taaki)
Merge pull request #24

9037707 Rewrite 5x52 normalize method to be faster (Peter Dettman)
Merge pull request #25

6d6102f A few improvements to the sqrt tests (Peter Dettman)
Do not free endomorphism constants when disabled