Rename crc functions to private namespace

Apparently we overlap with some gtk (?) crc32() functions, causing
ours to be called and subsequently crashing since the arguments
aren't the same.

Move everything to a fio_ protected namespace.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/crc/crc32.h b/crc/crc32.h
index d59a560..674057b 100644
--- a/crc/crc32.h
+++ b/crc/crc32.h
@@ -18,6 +18,6 @@
 #ifndef CRC32_H
 #define CRC32_H
 
-extern uint32_t crc32(const void * const, unsigned long);
+extern uint32_t fio_crc32(const void * const, unsigned long);
 
 #endif