Full uACPI implementation (#54)

* Full uACPI implementation

Most uACPI kernel APIs are stubbed out but they are not
essential for what we need, which is basically evaluating
AML methods to discover PCI root bridges and their resources

* Fix build on IA32

* Don't fully initialize uACPI unless absolutely needed

Main concern for doing that is that running AML might put the
hardware into a non-PC compatible state with no reliable way
to reverse that (as per comment on #54).

For now `acpi_init` only sets up "early table access", as it
previously did, to allow ACPI table enumeration, but if the need
arises one can call `acpi_full_init` to be able to call into
uACPI functions that require the namespace to be loaded and initialized.

* Fix code style

Author: 48cf

GNUmakefile

@@ -99,8 +99,9 @@ ifeq ($(ARCH),ia32)
     endif
     override CFLAGS += \
         -m32 \
-        -march=i386 \
-        -mno-80387
+        -march=i686 \
+        -mno-80387 \
+        -mno-mmx
     override LDFLAGS += \
         -Wl,-m,elf_i386
     override NASMFLAGS += \