Merge pull request !47 from LeonChan/master

1，VFS代码中不修改参数增加const修饰
2，fs_file_mapping.c: 增加安全函数的判空
3，path_cache.c: sizeof改为使用类型
4，fs_syscall.c: 对NULL解引用

close: I3UMWD
Signed-off-by: yansira <yansira@hotmail.com>

Merge pull request !41 from LeonChan/lc-master

1, this RomFS's codebase is Nuttx romfs, then it is compatible with
   Linux RomFS and you can create such a file system using the tool
   genromfs.
2, there are two major changes against with the original Nuttx romfs:
   1), it is memory-based: all contents of the fs are stored in the
       memory in the very first stage of "mount".
   2), this version of romfs is altered to be compatible with our
       version of VFS to take advantage of vnode cache and path cache.

close: #I3S0CP

Merge pull request !43 from JING/drv

Merge pull request !40 from Zhaotianyu/0510init_framework

Close #I3S5W4

Change-Id: If82ac10821da40d13cd4faf878d150019df43849

Merge pull request !39 from zhOu/master

close: #I3I768
Change-Id: I0f5fc0038cf7154b4f2e5afd8ecf767934e61e7c

Merge pull request !35 from 野生毛霉君/master

Change-Id: I05564abac3f0a8f7881ebe8b5b72c1b6abbbe448

Merge pull request !34 from li_zan/master

Merge pull request !32 from Far/dev

Merge pull request !33 from 野生毛霉君/master

Change-Id: Id5d0019550abb395d56b254d3eb260316fe983e4

Function VnodeInUseIter and VnodeFreeAll used to be recursive.
Now we traverse the current in-use vnode list to find the vnode in
1 filesystem

Close #I3NN3U

Merge pull request !15 from MGY917/master

Change-Id: Ia46512ceb07333b3c51ff57d41ef8993f1ca6495

Merge pull request !30 from Far/fatfs

Merge pull request !31 from 野生毛霉君/master

Change-Id: Ib99e937093336cfb16c44d0f811613d90f1b2f13

When tmpfs_lookup find a vnode from hashlist, the field parent of vnode should be updated,
because the old parent may be reclaimed.

Close #I3NNFA

Merge pull request !29 from LeonChan/lc-master

Close: I3NGBT
Change-Id: I0c3ae0f389cabccc6ffa7a79b96ba6b028168dca

Merge pull request !27 from Far/dev

Merge pull request !28 from JING/master

Close #I3MYP4

Change-Id: I03b19a74ae5340aa6c7cdc84d044c469873c1648

!26 [Desc] add debug code to fix bug: kernel crashed after rmdir the umounted folder, parentVnode->data null
Merge pull request !26 from LeonChan/lc-master

Change-Id: If876cf6e9cba695906fa4a562c34027bd044aed6

Merge pull request !25 from 野生毛霉君/master

Change-Id: I256c6d908bce019698d349456109c8437ba751fc

Merge pull request !24 from LeonChan/lc-master

Change-Id: Id48e780054f8df37e27acf2b5fdb700d01490160

Merge pull request !13 from 马明帅/add_issus_pr_template_for_master

Merge pull request !19 from ysy4tc3/dev