added test for __builtin_strlen

Author: totalspectrum

Test/Expect/stest299.pasm

@@ -0,0 +1,15 @@
+pub main
+  coginit(0, @entry, 0)
+dat
+	org	0
+entry
+
+_main
+	mov	outa, #261
+_main_ret
+	ret
+
+COG_BSS_START
+	fit	496
+	org	COG_BSS_START
+	fit	496

Test/stest299.c

@@ -0,0 +1,3 @@
+void main() {
+    _OUTA = __builtin_strlen("hello") | 0x100; 
+}