Function pointer naming

[SunSerega]

Currently, function pointers definitions are placed inside <command> and require full-on parsing to properly interpret, because there are no tags to separate parameters and return type.

Also, the cl_arm_printf extension requires its own function pointer type, but there is nowhere to define it in XML.

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So, I've added <type category="function"> tags. I've also merged function pointer types with the same parameters under a common name. Including cases where original spacing differs:

clEnqueueSVMFreeARM:

void * svm_pointers[], void *user_data

clEnqueueSVMFree:

void* svm_pointers[], void* user_data