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.c b/crc/crc32.c
index 4afed1a..657031d 100644
--- a/crc/crc32.c
+++ b/crc/crc32.c
@@ -73,7 +73,7 @@
   0xA2F33668, 0xBCB4666D, 0xB8757BDA, 0xB5365D03, 0xB1F740B4
 };
 
-uint32_t crc32(const void *buffer, unsigned long length)
+uint32_t fio_crc32(const void *buffer, unsigned long length)
 {
 	const unsigned char *cp = (const unsigned char *) buffer;
 	uint32_t crc = 0;