Remove lstringdup

lstringdup makes no sense because we have to allocate the underlying buffer beforehand.
Just create a new buffer and lstringcpy it.

Author: NJdevPro

spstring.h

@@ -64,7 +64,6 @@ size_t lstringcpy ( LString *dst, const LString *src );
 size_t lstringchcpy ( LString *dst, const char *src );
 size_t lstringcat ( LString *dst, const LString *src );
 size_t lstringchcat ( LString *dst, const char *src );
-LString lstringdup ( const LString *src );
 
 
 /* =================== Dynamic allocation on the Heap =======================