+ *) Add a new flag to memory BIOs, BIO_FLAG_MEM_RDONLY. This marks the BIO
+ as "read only": it can't be written to and the buffer it points to will
+ not be freed. Reading from a read only BIO is much more efficient than
+ a normal memory BIO. This was added because there are several times when
+ an area of memory needs to be read from a BIO. The previous method was
+ to create a memory BIO and write the data to it, this results in two
+ copies of the data and an O(n^2) reading algorithm. There is a new
+ function BIO_new_mem_buf() which creates a read only memory BIO from
+ an area of memory. Also modified the PKCS#7 routines to use read only
+ memory BIOSs.
+ [Steve Henson]
+