* add DECLARE_OVERLAP_INSN to bind instructions with extension
* add overlap_list.h to contain the declare of all overlapping instructions
* make func function for overlapping instruction return NULL when the coresponding
extension(s) is not supported.
Precompiled headers were broken because they weren't compiled with
the same -fPIC setting as the rest of the code. Fix by just making
everything use -fPIC.
Andrew Waterman
Weiwei Li
Chih-Min Chao