Added test for BASIC string constants

Author: totalspectrum

Test/Expect/basexec06.txt

@@ -15,3 +15,4 @@ p=91 b$=mval90
 100=$64
 
 64 bits: x=1234567890 y=1234567889999
+S=[hello]

Test/basexec06.bas

@@ -81,6 +81,12 @@ testread
 ' some basic 64 bit stuff
 test64bits
 
+' test constant strings
+const S1 = "hello"
+const S2 = S1
+
+doshow(@S2)
+
 ' and exit
 doexit 0
 
@@ -116,3 +122,7 @@ sub test64bits()
   print
   print "64 bits: x="; x; " y="; y
 end sub
+
+sub doshow(sp as const string ptr)
+  print "S=["; sp(0); "]"
+end sub