Add %A/%a uppercase/lowercase string format specifiers (#2165)

test/asm/string-formatting.asm

@@ -2,7 +2,7 @@ def n equ 300
 def m equ -42
 def f equ -123.0456
 def pi equ 3.14159
-def s equs "hello"
+def s equs "Hello!"
 def t equs "\"\\t\" is '\t'"
 def u equs "\t\r\0\n"
 
@@ -10,7 +10,8 @@ def u equs "\t\r\0\n"
 	println "<{u:m}> <{+3d:m}> <{#016o:m}>"
 	println "<{f:pi}> <{06.f:f}> <{.10f:f}>"
 	println "\"{#-20s:t}\", \"{#20s:t}\", \"{20s:t}\""
-	println "{#s:u}"
+	println "{s:s} {A:s} {a:s}"
+	println "{#s:u} {#A:u} {#a:u}"
 
 macro foo
 	println "\1 <{\1}>"