Allow building libdeflate without linking to any libc functions by using
'make FREESTANDING=1'. When using such a library build, the user will
need to call libdeflate_set_memory_allocator() before anything else,
since malloc() and free() will be unavailable.
[Folded in fix from Ingvar Stepanyan to use -nostdlib, and made
freestanding_tests() check that no libs are linked to.]
Update https://github.com/ebiggers/libdeflate/issues/62
Move program utility functions that are used only by "test programs"
(i.e. not by gzip/gunzip) from prog_util.{c,h} into test_util.{c,h}.
This reduces the code that is compiled for the default build target,
which excludes the test programs.
QueryPerformanceCounter() is much more accurate than
GetSystemTimeAsFileTime().
Also avoid converting into a specific time unit until the results need
to be displayed. This is more efficient and avoids losing precision.
* Bring in common headers and program code from xpack project
* Move program code to programs/
* Move library code to lib/
* GNU89 and MSVC2010 compatibility
* Other changes
