Fix the bug that cannot parse multi-level struct declaration

Indicate which part in the stack is used for the members of
current struct declaration, instead of all the stack in all cases.

Signed-off-by: Yicheng Qin <qycqycqycqycqyc@gmail.com>
Fix the bug that cannot handle undefined struct

1. Handle dump and load of undefined struct correctly.
2. Check undefine or not before the calcuation of struct size

Signed-off-by: Yicheng Qin <qycqycqycqycqyc@gmail.com>
Fix the incorrect conversion from TSTRING to TCDATA

TSTRING should be converted to TCDATA of c pointer which points to
the start character of the string.