Does it mean, that you get still compilation error with "ECDSA_SIG" (which i did not get)?
In case, you got an error in the steps in posting (4), we can try to debug where the version of OpenSSL is taken from by checking the .i file.
To produce the .i file from the "naviserver" directory, use:
gcc -save-temps -DNDEBUG -Wall -fPIC -pipe -I./include -I"/usr/src/tcl8.6.6/generic" -DHAVE_CONFIG_H -c -o nsd/tclcrypto.o nsd/tclcrypto.c
Note, one "." removed in the first "-I" flag
In case, the steps in posting (4) did not produce an error, NaviServer is installed already.
