card fixes and adjustments

[DacoTaco]

These are changes i found in GCMM that i merged back into libogc.
what this changes :

• fixes a bug Card_Create() fails when game share filename prefixes #113 ( thx suloku )
• small es.h/tmd typo
• expose get & set statusex through new functions
• introduce CARD_GetSerialNo & CARD_GetFreeBlocks
• make the internal read/write/erasesector functions not static so tools like GCMM can use them without needing a copy of card.c

i have a working GCMM fork that works with these changes, which i will upstream once this is merged.
so if there are any comments i can change it in GCMM at the same time :)