Add some unit-tests for Mid vb function (includes fdo#73771)

Change-Id: Ib5ee18207897cbe16a818096769cdb055dc9dad7
Reviewed-on: https://gerrit.libreoffice.org/7583Reviewed-by: Noel Power <noel.power@suse.com>
Tested-by: Noel Power <noel.power@suse.com>

basic/qa/basic_coverage/test_mid_EndOutOfBounds.vb

+'
+' This file is part of the LibreOffice project.
+'
+' This Source Code Form is subject to the terms of the Mozilla Public
+' License, v. 2.0. If a copy of the MPL was not distributed with this
+' file, You can obtain one at http://mozilla.org/MPL/2.0/.
+'
+
+Function doUnitTest as Integer
+    If (Mid("abc", 1, 4) = "abc") Then
+        doUnitTest = 1
+    Else
+        doUnitTest = 0
+    End If
+End Function

basic/qa/basic_coverage/test_mid_NoEnd.vb

+'
+' This file is part of the LibreOffice project.
+'
+' This Source Code Form is subject to the terms of the Mozilla Public
+' License, v. 2.0. If a copy of the MPL was not distributed with this
+' file, You can obtain one at http://mozilla.org/MPL/2.0/.
+'
+
+Function doUnitTest as Integer
+    If (Mid("abc", 2) = "bc") Then
+        doUnitTest = 1
+    Else
+        doUnitTest = 0
+    End If
+End Function

basic/qa/basic_coverage/test_mid_StartOutOfBounds.vb

+'
+' This file is part of the LibreOffice project.
+'
+' This Source Code Form is subject to the terms of the Mozilla Public
+' License, v. 2.0. If a copy of the MPL was not distributed with this
+' file, You can obtain one at http://mozilla.org/MPL/2.0/.
+'
+
+Function doUnitTest as Integer
+    If (Mid("abc", 5, 1) = "") Then
+        doUnitTest = 1
+    Else
+        doUnitTest = 0
+    End If
+End Function

basic/qa/basic_coverage/test_mid_first.vb

+'
+' This file is part of the LibreOffice project.
+'
+' This Source Code Form is subject to the terms of the Mozilla Public
+' License, v. 2.0. If a copy of the MPL was not distributed with this
+' file, You can obtain one at http://mozilla.org/MPL/2.0/.
+'
+
+Function doUnitTest as Integer
+    If (Mid("abc", 1, 1) = "a") Then
+        doUnitTest = 1
+    Else
+        doUnitTest = 0
+    End If
+End Function