x86_64-asm: =m operand fixes

The problem was with tcctest.c:

    unsigned set;
    __asm__("btsl %1,%0" : "=m"(set) : "Ir"(20) : "cc");

when with tcc compiled with the HAVE_SELINUX option, run with
tcc -run, it would use large addresses far beyond the 32bits
range when tcc did not use the pc-relative mode for accessing
'set' in global data memory.  In fact the assembler did not
know about %rip at all.

Changes:
- memory operands use (%rax) not (%eax)
- conversion from VT_LLOCAL: use type VT_PTR
- support 'k' modifier
- support %rip register
- support X(%rip) pc-relative addresses

The test in tcctest.c is from Michael Matz.

Makefile

@@ -176,7 +176,7 @@ $(ARM64_CROSS): $(ARM64_FILES)
 # libtcc generation and test
 ifndef ONE_SOURCE
 LIBTCC_OBJ = $(filter-out tcc.o,$(patsubst %.c,%.o,$(filter %.c,$(NATIVE_FILES))))
-LIBTCC_INC = $(filter %.h,$(CORE_FILES)) $(filter-out $(CORE_FILES),$(NATIVE_FILES))
+LIBTCC_INC = $(filter %.h,$(CORE_FILES)) $(filter-out $(CORE_FILES) i386-asm.c,$(NATIVE_FILES))
 else
 LIBTCC_OBJ = libtcc.o
 LIBTCC_INC = $(NATIVE_FILES)