Created wrapper functions loader_alloc, loader_calloc, loader_free,
and loader_realloc. Made the existing loader allocation functions use
them. Replaced manual usage of VkAllocatorCallbacks with the new
wrapper functions.
Added FreeBSD in supported platforms in vk_loader_platform.h, and tests,
defined BSD_VISIBLE and included some necessary header files for
Vulkan-Loader to compile on FreeBSD.
v2: did the same in loader/loader.c (Charles Giessen)
v3: did the same in the tests (Charles Giessen)
v4: applied this downstream patch from Jan Beich because there's no /proc
on FreeBSD: https://github.com/freebsd/freebsd-ports/blob/7caf52e37ba2174dc50a7440d63eec70d7d58ebc/graphics/vulkan-loader/files/patch-loader_vk__loader__platform.h (Jan Beich)
v4: rebased to master and modified tests/loader_regression_tests.cpp,
tests/loader_testing_main.cpp
v5: moved the definition of __BSD_VISIBLE 1 (required for alloca to
work) in CMakeLists.txt from header files (Charles Giessen)
v6: replaced ${CMAKE_SYSTEM_NAME} with CMAKE_SYSTEM_NAME in
loader/CMakeLists.txt to match the style of previous checks (Jan Beich)
v7: replaced add_compile_definitions with target_compile_definitions to
prevent the macro from being applied unnecessarily (Charles Giessen)
Andrew Naumov