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/crc16.c b/crc/crc16.c
index d9c4e49..f593f71 100644
--- a/crc/crc16.c
+++ b/crc/crc16.c
@@ -43,7 +43,7 @@
 	0x8201, 0x42C0, 0x4380, 0x8341, 0x4100, 0x81C1, 0x8081, 0x4040
 };
 
-unsigned short crc16(const void *buffer, unsigned int len)
+unsigned short fio_crc16(const void *buffer, unsigned int len)
 {
 	const unsigned char *cp = (const unsigned char *) buffer;
 	unsigned short crc = 0;