fixup! mingw: support long paths

In 4d3d891493 (squash! Win32: add a cache below mingw's lstat and
dirent implementations, 2013-10-01), we adjusted the FSCache feature to
accommodate for the `en/fill-directory-fixes` patches, which insist on
POSIX-like semantics where `struct dirent`'s `name` entry must be a
`char` array and cannot be a `char` pointer.

However, when squashing this adjustment into the appropriate patch
during the nex rebase (which resulted in 1fcade1d98 (mingw: add a cache
below mingw's lstat and dirent implementations, 2013-10-01)), this
developer failed to split out the `MAX_LONG_PATH` part into the
appropriate patch but by mistake dropped it instead.

This patch fixes that, addressing
https://github.com/git-for-windows/git/issues/2494.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

compat/win32/fscache.c

@@ -73,7 +73,7 @@ struct fsentry {
 
 struct heap_fsentry {
 	struct fsentry ent;
-	char dummy[MAX_PATH];
+	char dummy[MAX_LONG_PATH];
 };
 
 /*