Added support for public keys.

Fixed possible leak.

When using libaacs with mythtv I was getting the following crash:
  Program received signal SIGSEGV, Segmentation fault.
  0xb052085a in yylex () from /usr/lib/dri/i965_dri.so
  (gdb) bt
  #0  0xb052085a in yylex () from /usr/lib/dri/i965_dri.so
  #1  0xafe1529a in yyparse (scanner=0xafd24b48, dklist=0xafd3fa60, pklist=0xae054a70, clist=0xafd39af8, celist=0xae086908, dkplist=0x0) at keydbcfg-parser.c:1537
        #2  0xafe15a22 in keydbcfg_parse_config (cfgfile=0xae036898, path=0xae0517c8 "/var/lib/mythtv/.mythtv/KEYDB.cfg") at file/keydbcfg-parser.y:440

Obviously the linker has picked the wrong yylex.

I solved this with the following patch which renames all the yy* symbols
to libaacs_yy*.

NOTE: DOES NOT SEARCH FROM ~/.libaacs/ or /etc/aacs/ ANYMORE !

(AACS spec, section 4.3, steps 23-24)

Make sure all fields are initialized even if some parameters are not given

Removed (unused) crypto_randomize()

This function is used when creating ECDSA key pairs.

(gcrypt does not export any elliptic curve functions.
Creating ECDSA key pair using AACS curve parameters is impossible
with current libcrypt API.)

Renamed parameters

Note: completely untested!