Move all GAS directives under TOK_ASMDIR prefix to include leading '.'

Use only these tokens in `asm_parse_directive` and don't recycle others' tokens (like TOK_SECTION1)

tcc.h

@@ -956,7 +956,9 @@ struct TCCState {
 
 #define DEF_ASM(x) DEF(TOK_ASM_ ## x, #x)
 #define TOK_ASM_int TOK_INT
-#define TOK_ASM_weak TOK_WEAK1
+#define DEF_ASMDIR(x) DEF(TOK_ASMDIR_ ## x, "." #x)
+#define TOK_ASMDIR_FIRST TOK_ASMDIR_byte
+#define TOK_ASMDIR_LAST TOK_ASMDIR_section
 
 #if defined TCC_TARGET_I386 || defined TCC_TARGET_X86_64
 /* only used for i386 asm opcodes definitions */