add c decl stuff to crc32.h

stasis/crc32.h

@@ -1,5 +1,6 @@
 #ifndef STASIS_CRC32_H
 #define STASIS_CRC32_H
+
 /* This CRC code was taken from: http://www.axlradius.com/freestuff/crc2.c
 
    (It is presumably in the public domain.  Other files under /freestuff/ are...)
@@ -16,5 +17,10 @@
    crc = crc32(buffer, length, crc)
 */
 #include <stasis/common.h>
+
+BEGIN_C_DECLS
+
 uint32_t stasis_crc32(const void *buffer, unsigned int count, uint32_t crc);
+
+END_C_DECLS
 #endif // STASIS_CRC32_H