solve a crash problem and a memory leak problem

[booknouse]

psf.cc,remote redundant close in destructor,because it would be called in ~PSFFile.psfile.cc, use new validate method, and add m_buffer's NULL judgement to Make the close method reentrant(cause crash).psfinternal.h, add ~PropertyBlock method, new validate method to PSFFile and change m_size to ssize_t.psfpropertyblock.cc, delete pointers in m_propmap to avoid memory leaks.