as: add some test cases under test/

TODO

@@ -21,6 +21,12 @@ Tools:
 - readelf: add support for relocs
 - readelf: add support for program headers
 - as:
+  * support .ident:
+    + change strtab to have a finalizer which returns an image array,
+    + use standard output_section for strtab
+    + move strtab to tunit
+    + have .ident append string to .comment strtab
+    + finalize .comment strtab before output()
   * add support for named sections
   * add support for sub-sections
   * add support for data directives (.word, .asciz, etc)

as/test/test1.s

@@ -0,0 +1,6 @@
+	.text
+	.globl start
+start:
+	movei 1,0
+	jsys 94
+	halt

as/test/test2.c

@@ -0,0 +1 @@
+int foo(void) { return 27; }

as/test/test2.s

@@ -0,0 +1,10 @@
+	.file	"z.c"
+	.text
+	.globl	foo
+	.type	foo, @function
+foo:
+	movei 1,33
+	popj 017,
+	.size	foo, .-foo
+	.ident	"GCC: (GNU) 4.3.0.- for XKL-2 (XKL LLC, Kirkland, WA, USA)  Built 2013-08-15 23:03 +0200 on porter by mikpe"
+	.section	.note.GNU-stack,"",@progbits