Changed 'Requires' to 'Requires.private'.

Only static builds need to link against the crypto libs.

libssh2.pc.in

@@ -11,7 +11,7 @@ Name: libssh2
 URL: http://www.libssh2.org/
 Description: Library for SSH-based communication
 Version: @LIBSSH2VER@
-Requires: @LIBSREQUIRED@
+Requires.private: @LIBSREQUIRED@
 Libs: -L${libdir} -lssh2 @LDFLAGS@ @LIBS@
 Libs.private: @LIBS@
 Cflags: -I${includedir}