Warnings from Volk with higher warnings enabled

[gruelingpine185]

The same problem regarding other functions was previously addressed in #11. I'm new to Vulkan, Volk, and the whole graphics and rendering thing, so I'm not sure if this was intensional or not. Anyways, here is the relevant part from compiling Volk with -std=c11 -O2 -Wall -Wextra -pedantic. Oh, and this is using the sdk-1.3.250 branch.

# ...
vendor/volk/volk.c:113:33: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
VkInstance volkGetLoadedInstance()
                                ^
                                 void
vendor/volk/volk.c:124:29: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
VkDevice volkGetLoadedDevice()
                            ^
                             void
2 warnings generated.

[zeux]

Thanks! This is now fixed in master.