Type issues

[th3or14]

1. VkBool32 presentSupport should be assigned to VK_FALSE instead of false in VkBootstrap.cpp.

2. VkAllocationCallbacks* allocation_callbacks should be assigned to nullptr instead of VK_NULL_HANDLE in VkBootstrap.h because callbacks are pointers, not handles.

3. The problem of usage of VkBool32 in VkBootstrap.h and VkBootstrap.cpp for fields is in such initialization:

memset(fields, UINT8_MAX, sizeof(VkBool32) * field_capacity);

After setting every byte to 0xFF (UINT8_MAX), every VkBool32 field becomes 0xFFFFFFFF.

While boolean context works as expected in the current code for fields initalized in such a way, a comparison against VK_TRUE would fail because VK_TRUE (1U) is not equal to 0xFFFFFFFF, which sounds bad for a field of type VkBool32 even though there are currently no comparisons against VK_TRUE.

I would simply change the type of fields from VkBool32 to uint8_t. Then when fields become "enabled" after setting every byte to UINT8_MAX, they don't have to be equal to VK_TRUE because the type is not VkBool32. Boolean context should still work as expected.