cortex-r4: add __rt_ffs
cortex-r4: wrap asm functions with .asmfunc/.endasmfunc
rm48x50: add cache_{enable, disable}
RM48 does not have cache implemented
rm48x50: rt_interrupt_nest should be `volatile rt_uint8_t`
Merge pull request #109 from grissiom/rm48x50

Rm48x50
tools: add an option to generate cscope database

When --cscope option is given to Scons, it will generate a cscope
cross-reference database in current directory, which is useful in
Vim(and other cscope-aware text editors). For example, `scons -s
--cscope` will do nothing except generating the database. You can use
this option with other options together.

It is inspired by the `make cscope` of Linux.
Merge pull request #110 from grissiom/cscope

tools: add an option to generate cscope database
update libcpu/arm/cortex-m4: restore MSP.
update libcpu/arm/cortex-m3: restore MSP.
update libcpu/arm/cortex-m0: restore MSP.
Merge pull request #108 from aozima/pulls

回收main函数所用的栈空间
update iar.py: fixed bug when path is absolute.
Add component initialization define in rtdef.h
Merge branch 'master' of https://github.com/RT-Thread/rt-thread
Add component initialization.
fix compiling error
fix compiling warning
format code by Astyle.
fixed bug: correct cortex-m SCB->VTOR address.