[mini] Rename & expose a few functions to mini.h.

[mini] Rename & expose a few functions to mini.h.

This adds to mini.h & fixes naming of the following functions:
	emit_get_gsharedvt_info_klass
	mono_emit_calli
	get_memcpy_method
	get_memset_method
	emit_memory_barrier
	emit_runtime_constant
	mini_class_check_context_used
	mono_emit_wb_aware_memcpy
	emit_write_barrier

Those functions will be used later by the memory access functions to be extracted out of method-to-ir.c