Pullreq FAT improvements
* NuttX: Add CONFIG_FAT_LFN_ALIAS_HASH to speed up creating long filenames.
Long filenames on FAT filesystems have associated 8.3 character alias
short filenames. The traditional form of these is FILENA~1.EXT with
a running count of the number of similar names. However creating this
unique count can take several seconds if there are many similarly named
files in the directory. Enabling FAT_LFN_ALIAS_HASH uses an alternative
format of FI0123~1.TXT where the four digits are a hash of the original
filename. This method is similar to what is used by Windows 2000 and
later.
* NuttX: Add CONFIG_FAT_LFN_ALIAS_TRAILCHARS alternative format for 8.3 filenames.
Traditional format for long filename 8.3 aliases takes first 6
characters of long filename. If this option is set to N > 0,
NuttX will instead take first 6-N and last N characters to form
the short name. This is useful for filenames like "datafile12.txt"
where the first characters would always remain the same.
* NuttX: FAT32: Fix file date corruption in fat_truncate().
* NuttX: if SD card wait seems to be a long one, give time for other threads to run.
Approved-by: GregoryN <gnutt@nuttx.org>
