MumbleSSL (defined in SSL.h/.cpp) uses OpenSSL functions - starting with
SSL_library_init. These functions are defined in the ssleay32 library.
This library was missing, which resulted/could result in linker errors
(in specific kinds of build environments).
is in CONFIG.
This fixes a problem I encountered where including openssl.pri
in TestCryptographicHash.pro on Qt 4 wouldn't link OpenSSL.
This commit fixes that problem by ensuring link_pkgconfig is
always included in CONFIG when openssl.pri uses pkgconfig.