CPU and memory controller endian changes.

===============
Rairii changes:

memctrlbase: The memory controller may have an endian swap mode.
mpc106: Only mmio regions need endian swap and only if PCIR_LE_MODE is
set.

videoctrl: Add framebuffer_in_main_memory flag. Use needs_swap_endian.

debugger: Fix disasm for little endian mode.

ppcmmu: little endian mode requires munging of the data and instruction
addresses, affecting the 3 least significant bits.

ppcexec: pc_real is always recalculated during little endian mode
because instructions are swapped every 8 bytes (due to the address
munging).

==============
joevt changes:

Add SUPPORTS_MEMORY_CTRL_ENDIAN_MODE for memory controller.
Use cmake -DDPPC_SUPPORT_PPC_LE=ON to enable.

Add SUPPORTS_PPC_LITTLE_ENDIAN_MODE for CPU.
Use cmake -DDPPC_SUPPORT_MEM_LE=ON to enable.

Add ppc_change_endian to handle endian switch for MPC601 (uses HID0
instead of MSR) and later PPC CPUs.

Add is_LE flag to ppc_state to indicate little endian mode for all
processor versions.

Create separate ppc_exec_inner template functions for little and big
endian.

Switch endian mode in the ppc_exec outer functions when power_off_reason
is po_endian_switch.

Since MPC601 doesn't have ILE and LE bits, remove that code for that
CPU.

videoctrl: Uses templated methods. See next commit for a fix that this
change introduces.

debugger/debugger.cpp

@@ -430,6 +430,21 @@ static uint32_t disasm(PPCDisasmContext &ctx) {
     cout << COUT08X << ctx.instr_addr;
     cout << ": " << COUT08X << ctx.instr_code;
     cout << "    " << disassemble_single(&ctx) << setfill(' ') << right << dec;
+
+#if SUPPORTS_MEMORY_CTRL_ENDIAN_MODE
+    bool needs_swap = false;
+    if (mem_ctrl_instance != nullptr)
+        needs_swap = mem_ctrl_instance->needs_swap_endian(false);
+#endif
+
+    uint32_t phys_addr;
+    uint8_t* real_addr = mmu_translate_imem(ctx.instr_addr, &phys_addr);
+    ctx.instr_code =
+#if SUPPORTS_MEMORY_CTRL_ENDIAN_MODE
+        needs_swap ? READ_DWORD_LE_A(real_addr) :
+#endif
+        READ_DWORD_BE_A(real_addr);
+
     return ctx.instr_addr;
 }