kvm: libkvm: move kvm_context to kvm-common.h & add CFLAGS to config-* filese

kvm: libkvm: move kvm_context to kvm-common.h & add CFLAGS to config-* filese

This patch moves kvm_context from libkvm.c to kvm-common.h. This is so
other files are able to see members of kvm_context. Also you should
allways declare stuff like this in a header anyway.

Also moved are delcrations MAX_VCPU, KVM_MAX_NUM_MEM_REGIONS
to kvm-common.h. While PAGE_SIZE & PAGE_MASK where moved to kvm-x86.h.

The idea here is kvm-$(ARCH).h will be headers for interal use by
libkvm. Headers name libkvm-$(ARCH) will be functions that are
arch specific that will be exposed to a user.

Also apart of this patch is added CFLAGS to the config-$(ARCH).mak files.
Really instead there needed to be a unified make file for libkvm &
user directory. But for now this fixes the issue

Signed-off-by: Jerone Young <jyoung5@us.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>