doc: Fix documentation of EVP_EncryptUpdate().
The documentation was off by one for the length this function could return.
@@ -210,10 +210,15 @@ specified.
EVP_EncryptUpdate() encrypts B<inl> bytes from the buffer B<in> and
writes the encrypted version to B<out>. This function can be called
multiple times to encrypt successive blocks of data. The amount
-of data written depends on the block alignment of the encrypted data:
-as a result the amount of data written may be anything from zero bytes
-to (inl + cipher_block_size - 1) so B<out> should contain sufficient
-room. The actual number of bytes written is placed in B<outl>. It also
+of data written depends on the block alignment of the encrypted data.
+For most ciphers and modes, the amount of data written can be anything
+from zero bytes to (inl + cipher_block_size - 1) bytes.
+For wrap cipher modes, the amount of data written can be anything
+from zero bytes to (inl + cipher_block_size) bytes.
+For stream ciphers, the amount of data written can be anything from zero
+bytes to inl bytes.
+Thus, B<out> should contain sufficient room for the operation being performed.
+The actual number of bytes written is placed in B<outl>. It also
checks if B<in> and B<out> are partially overlapping, and if they are
0 is returned to indicate failure.
