Update libglnx, port various bits to new API

Using the error prefixing in the delta processing allows us to
do new code style.  Also strip trailing whitespace.

Use error prefixing in a few other random places.  I didn't
hunt for all of them, just testing out the new API.

Use `glnx_fchmod()`.  Also note I dropped one `fchmod (tmpf, 0600)`
which is no longer necessary.

Update submodule: libglnx

Closes: #1011
Approved by: jlebon

src/libostree/ostree-repo-commit.c

@@ -253,8 +253,8 @@ commit_loose_regfile_object (OstreeRepo        *self,
       if (S_ISREG (mode))
         {
           const mode_t content_mode = (mode & (S_IFREG | 0775)) | S_IRUSR;
-          if (fchmod (tmpf->fd, content_mode) < 0)
-            return glnx_throw_errno_prefix (error, "fchmod");
+          if (!glnx_fchmod (tmpf->fd, content_mode, error))
+            return FALSE;
         }
       else
         g_assert (S_ISLNK (mode));
@@ -266,8 +266,8 @@ commit_loose_regfile_object (OstreeRepo        *self,
         return glnx_throw (error, "Invalid mode 0%04o with bits 0%04o in bare-user-only repository",
                            mode, invalid_modebits);
 
-      if (fchmod (tmpf->fd, mode) < 0)
-        return glnx_throw_errno_prefix (error, "fchmod");
+      if (!glnx_fchmod (tmpf->fd, mode, error))
+        return FALSE;
     }
 
   if (_ostree_repo_mode_is_bare (self->mode))
@@ -495,8 +495,8 @@ create_regular_tmpfile_linkable_with_content (OstreeRepo *self,
         }
     }
 
-  if (fchmod (tmpf.fd, 0644) < 0)
-    return glnx_throw_errno_prefix (error, "fchmod");
+  if (!glnx_fchmod (tmpf.fd, 0644, error))
+    return FALSE;
 
   *out_tmpf = tmpf; tmpf.initialized = FALSE;
   return TRUE;
@@ -653,8 +653,8 @@ write_content_object (OstreeRepo         *self,
       if (!g_output_stream_flush (temp_out, cancellable, error))
         return FALSE;
 
-      if (fchmod (tmpf.fd, 0644) < 0)
-        return glnx_throw_errno_prefix (error, "fchmod");
+      if (!glnx_fchmod (tmpf.fd, 0644, error))
+        return FALSE;
     }
 
   const char *actual_checksum = NULL;
@@ -852,8 +852,8 @@ write_metadata_object (OstreeRepo         *self,
     return FALSE;
   if (glnx_loop_write (tmpf.fd, bufp, len) < 0)
     return glnx_throw_errno_prefix (error, "write()");
-  if (fchmod (tmpf.fd, 0644) < 0)
-    return glnx_throw_errno_prefix (error, "fchmod");
+  if (!glnx_fchmod (tmpf.fd, 0644, error))
+    return FALSE;
 
   /* And commit it into place */
   if (!_ostree_repo_commit_tmpf_final (self, actual_checksum, objtype,