Import private key in to ecc_key

[naushadck]

By using ecc_ansi_x963_import, we can import public key in to ecc_key.
However, unable to import private key in to ecc-key.

Any example exists.

[sjaeckel]

libtomcrypt/doc/crypt.tex

Lines 5776 to 5777 in b1fa61d

	The ECC key pointed to by \textit{key} is exported in public fashion to the array pointed to by \textit{out}. The ANSI X9.63 format used is from
	section 4.3.6 of the standard. It does not allow for the export of private keys.

[naushadck]

ecc_ansi_x963_import works for public key only. Does not work for private key.