GetPointerTo(): _only_ get pointer, never data

Previously this evaluated the variable and returned its string representation - which contains up to print elements data, and converting this may also raise UnicodeDecodeErrors (which was the actual reason for me to catch that); then threw all the converted data away using a matcher.

The new code checks for the address of the data and uses this after converting it by GDB to an unsigned integer - the data is never accessed or converted. This may also provide a speedup.