Use static libcurl, dynamic OpenSSL.

This links libcurl statically, removing the need for three of five DLLs.
OpenSSL is required for other things and I haven't found a way to link
that statically. Right now libeay32.DLL and ssleay32.DLL remain as
dependencies.

libcurl is built thusly:
git clone https://github.com/bagder/curl.git
cd curl
buildconf.bat
cd winbuild
nmake /f Makefile.vc mode=static WITH_SSL=static \
 WITH_DEVEL=%OPENSSL_ROOT% VC=10 ENABLE_SSPI=no ENABLE_IDN=no \
 ENABLE_WINSSL=no DEBUG=no MACHINE=x86 GEN_PDB=no ENABLE_IPV6=yes

where OPENSSL_ROOT is the path to the OpenSSL root directory gotten
from http://slproweb.com/products/Win32OpenSSL.html