cparser: refactor ctype module & add function pointer support

* refactor
  * move cparser related headers into userspace/ffi folder
  * ctype stack related functions are moved into a separate module
  * introduce stack frame to help parsing function pointers
  * rename ctype_stack_* prefix to cp_ctstk_*
* add function pointer support

Signed-off-by: Qingping Hou <qingping.hou@gmail.com>
add large_struct test

Signed-off-by: Qingping Hou <qingping.hou@gmail.com>
use unnamed_counter as unique id for unnamed type

Using line number will confuse the parser if there were multiple
unnamed types in the same line.

Signed-off-by: Qingping Hou <qingping.hou@gmail.com>
add test_cparser target for ffi_test Makefile

Signed-off-by: Qingping Hou <qingping.hou@gmail.com>