added txt.rvs_on() and txt.rvs_off(), added txt.color() support for virtual target

compiler/res/prog8lib/shared_cbm_textio_functions.p8

@@ -23,6 +23,14 @@ txt {
         chrout(' ')
     }
 
+    sub rvs_on() {
+        txt.chrout(18)
+    }
+
+    sub rvs_off() {
+        txt.chrout(146)
+    }
+
 
     asmsub  print (str text @ AY) clobbers(A,Y)  {
     	; ---- print zero terminated string, in PETSCII encoding, from A/Y

compiler/res/prog8lib/virtual/textio.p8

@@ -53,6 +53,21 @@ sub uppercase() {
     ; not supported
 }
 
+sub rvs_on() {
+    print("\x1b[7m")
+}
+
+sub rvs_off() {
+    print("\x1b[0m")
+}
+
+sub color (ubyte txtcol) {
+    print("\x1b[3")
+    chrout('0' + txtcol)
+    chrout('m')
+}
+
+
 sub chrout(ubyte char) {
     %ir {{
         loadm.b r99100,txt.chrout.char