refactor: the long goodbye

long is 32 bits on windows, while it is 64 bits on other architectures.
This makes the type suboptimal for a codebase meant to be
cross-platform. Replace it with more appropriate integer types.

src/nvim/memfile.c

@@ -125,7 +125,7 @@ memfile_T *mf_open(char *fname, int flags)
   // must be rounded up.
   if (mfp->mf_fd < 0
       || (flags & (O_TRUNC|O_EXCL))
-      || (size = vim_lseek(mfp->mf_fd, 0L, SEEK_END)) <= 0) {
+      || (size = vim_lseek(mfp->mf_fd, 0, SEEK_END)) <= 0) {
     // no file or empty file
     mfp->mf_blocknr_max = 0;
   } else {