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/crc7.c b/crc/crc7.c
index 47aa332..bf7fd1c 100644
--- a/crc/crc7.c
+++ b/crc/crc7.c
@@ -43,7 +43,7 @@
 	0x46, 0x4f, 0x54, 0x5d, 0x62, 0x6b, 0x70, 0x79
 };
 
-unsigned char crc7(const unsigned char *buffer, unsigned int len)
+unsigned char fio_crc7(const unsigned char *buffer, unsigned int len)
 {
 	unsigned char crc = 0;