compress: Drop lz4 includes from compress.h

The lz4 functions are only used in test-compress.c, so let's just
put the declarations and includes in there instead of having everyone
including compress.h pull in the lz4 headers.

src/basic/compress.h

@@ -6,11 +6,6 @@
 #include <stdint.h>
 #include <unistd.h>
 
-#if HAVE_LZ4
-#include <lz4.h>
-#include <lz4frame.h>
-#endif
-
 #include "dlfcn-util.h"
 
 typedef enum Compression {
@@ -73,11 +68,6 @@ int decompress_stream_lz4(int fdf, int fdt, uint64_t max_size);
 int decompress_stream_zstd(int fdf, int fdt, uint64_t max_size);
 
 #if HAVE_LZ4
-extern DLSYM_PROTOTYPE(LZ4_compress_default);
-extern DLSYM_PROTOTYPE(LZ4_decompress_safe);
-extern DLSYM_PROTOTYPE(LZ4_decompress_safe_partial);
-extern DLSYM_PROTOTYPE(LZ4_versionNumber);
-
 int dlopen_lz4(void);
 #endif