Changes:
- geotiff.h: more precise signature for GTIFDirectoryInfo()
- applygeo.c/geotifcp.c: use uint16/32_t instead of old libtiff non _t custom types
- Bump CMake min to 3.0.0 and remove apparently unneeded cmake_policy() declarations
- CMake: remove libjpeg and libz from linking of libgeotiff itself.
- geo_config.h: prefix HAVE_xxx and restrict it to GEOTIFF_HAVE_STRINGS_H (fixes #61)
- GTIFPrintDefn(): avoid potential nullptr deref. CID 1469240
- CMake: use variable for installation subdirectories, and make sure INTERFACE_INCLUDE_DIRECTORIES is exported (fixes #67)
- ReadKey(): only allow reading a key with TIFFTagLocation=0 that has a count of 1 to avoid reading an illegal address (and crashing) when using GTIFKeyGet() or PrintKey() (fixes #66)
- ReadKey(): add extra warning messages
- CMake: avoid INTERFACE_LINK_LIBRARIES vs LINK_INTERFACE_LIBRARIES_DEBUG warning about TIFF
- CMake: Fix dllexport
- CMake: Revise exported cmake config wrt BUILD_SHARED_LIBS
- CMake: Revise exported cmake config wrt dependencies
- CMake: Respect _FIND_QUIETLY