Fix gcc-6 compilation errors; bug 594176

--- a/classes/tdesktop.cc
+++ b/classes/tdesktop.cc
@@ -26,6 +26,10 @@ Modified cursor behavior while desktop locked by Salvador E. Tropea (SET)
 #define Uses_TVCodePage
 #include <tv.h>
 
+#include <cmath>
+
+using std::abs;
+
 TDeskInit::TDeskInit( TBackground *(*cBackground)( TRect ) ) :
     createBackground( cBackground )
 {
--- a/classes/tdisplay.cc
+++ b/classes/tdisplay.cc
@@ -22,6 +22,10 @@ same used in original Turbo Vision for compatibility purposes.
 #define Uses_TVCodePage
 #include <tv.h>
 
+#include <cmath>
+
+using std::abs;
+
 // Remove me please!
 int TDisplay::dual_display=0;
 
--- a/classes/tvtext1.cc
+++ b/classes/tvtext1.cc
@@ -110,8 +110,8 @@
 char TCheckBoxes::button[] = " [ ] ";
 char TCheckBoxes::obutton[] = " [ ] ";
 
-TScrollChars TScrollBar::vChars = {30, 31, 177, 254, 178};
-TScrollChars TScrollBar::ovChars = {30, 31, 177, 254, 178};
-TScrollChars TScrollBar::hChars = {17, 16, 177, 254, 178};
-TScrollChars TScrollBar::ohChars = {17, 16, 177, 254, 178};
+TScrollChars TScrollBar::vChars = {30, 31, (char) 177, (char) 254, (char) 178};
+TScrollChars TScrollBar::ovChars = {30, 31, (char) 177, (char) 254, (char) 178};
+TScrollChars TScrollBar::hChars = {17, 16, (char) 177, (char) 254, (char) 178};
+TScrollChars TScrollBar::ohChars = {17, 16, (char) 177, (char) 254, (char) 178};
 
--- a/classes/x11/x11src.cc
+++ b/classes/x11/x11src.cc
@@ -94,6 +94,10 @@
  #define TIMER_ALARM SIGALRM
 #endif
 
+#include <cmath>
+
+using std::abs;
+
 const unsigned foWmin=5, foHmin=7, foWmax=20, foHmax=32;
 const int cursorDelay=300000;
 
@@ -2555,49 +2559,49 @@ Cursor TScreenX11::busyCursor,
        TScreenX11::leftPtr;
 char   TScreenX11::busyCursorMap[]=
 {
- 0xff, 0xff, 0xff, 0x1f,
- 0xfd, 0xff, 0xff, 0x1f,
- 0xf9, 0xff, 0xff, 0x1f,
- 0xf1, 0xff, 0xff, 0x1f,
- 0xe1, 0x7f, 0xc0, 0x1f,
- 0xc1, 0x7f, 0xc0, 0x1f,
- 0x81, 0x3f, 0x80, 0x1f,
- 0x01, 0x9f, 0x3b, 0x1f,
- 0x01, 0xce, 0x7b, 0x1e,
- 0xc1, 0xef, 0xfb, 0x1e,
- 0xc9, 0xef, 0xf1, 0x18,
- 0x9d, 0xef, 0xf1, 0x18,
- 0x9f, 0xef, 0xfe, 0x18,
- 0x3f, 0x6f, 0xff, 0x1e,
- 0x3f, 0xcf, 0x7f, 0x1e,
- 0xff, 0x9f, 0x3f, 0x1f,
- 0xff, 0x3f, 0x80, 0x1f,
- 0xff, 0x7f, 0xc0, 0x1f,
- 0xff, 0x7f, 0xc0, 0x1f,
- 0xff, 0xff, 0xff, 0x1f
+ (char)0xff, (char)0xff, (char)0xff, (char)0x1f,
+ (char)0xfd, (char)0xff, (char)0xff, (char)0x1f,
+ (char)0xf9, (char)0xff, (char)0xff, (char)0x1f,
+ (char)0xf1, (char)0xff, (char)0xff, (char)0x1f,
+ (char)0xe1, (char)0x7f, (char)0xc0, (char)0x1f,
+ (char)0xc1, (char)0x7f, (char)0xc0, (char)0x1f,
+ (char)0x81, (char)0x3f, (char)0x80, (char)0x1f,
+ (char)0x01, (char)0x9f, (char)0x3b, (char)0x1f,
+ (char)0x01, (char)0xce, (char)0x7b, (char)0x1e,
+ (char)0xc1, (char)0xef, (char)0xfb, (char)0x1e,
+ (char)0xc9, (char)0xef, (char)0xf1, (char)0x18,
+ (char)0x9d, (char)0xef, (char)0xf1, (char)0x18,
+ (char)0x9f, (char)0xef, (char)0xfe, (char)0x18,
+ (char)0x3f, (char)0x6f, (char)0xff, (char)0x1e,
+ (char)0x3f, (char)0xcf, (char)0x7f, (char)0x1e,
+ (char)0xff, (char)0x9f, (char)0x3f, (char)0x1f,
+ (char)0xff, (char)0x3f, (char)0x80, (char)0x1f,
+ (char)0xff, (char)0x7f, (char)0xc0, (char)0x1f,
+ (char)0xff, (char)0x7f, (char)0xc0, (char)0x1f,
+ (char)0xff, (char)0xff, (char)0xff, (char)0x1f
 };
 char TScreenX11::busyCursorMask[]=
 {
- 0xfc, 0xff, 0xff, 0x1f,
- 0xf8, 0xff, 0xff, 0x1f,
- 0xf0, 0xff, 0xff, 0x1f,
- 0xe0, 0x3f, 0x80, 0x1f,
- 0xc0, 0x3f, 0x80, 0x1f,
- 0x80, 0x3f, 0x80, 0x1f,
- 0x00, 0x1f, 0x00, 0x1f,
- 0x00, 0x0e, 0x00, 0x1e,
- 0x00, 0x04, 0x00, 0x1c,
- 0x00, 0x04, 0x00, 0x10,
- 0x80, 0x07, 0x00, 0x10,
- 0x08, 0x07, 0x00, 0x10,
- 0x0c, 0x07, 0x00, 0x10,
- 0x1f, 0x06, 0x00, 0x10,
- 0x1f, 0x06, 0x00, 0x1c,
- 0x3f, 0x0f, 0x00, 0x1e,
- 0xff, 0x1f, 0x00, 0x1f,
- 0xff, 0x3f, 0x80, 0x1f,
- 0xff, 0x3f, 0x80, 0x1f,
- 0xff, 0x3f, 0x80, 0x1f
+ (char)0xfc, (char)0xff, (char)0xff, (char)0x1f,
+ (char)0xf8, (char)0xff, (char)0xff, (char)0x1f,
+ (char)0xf0, (char)0xff, (char)0xff, (char)0x1f,
+ (char)0xe0, (char)0x3f, (char)0x80, (char)0x1f,
+ (char)0xc0, (char)0x3f, (char)0x80, (char)0x1f,
+ (char)0x80, (char)0x3f, (char)0x80, (char)0x1f,
+ (char)0x00, (char)0x1f, (char)0x00, (char)0x1f,
+ (char)0x00, (char)0x0e, (char)0x00, (char)0x1e,
+ (char)0x00, (char)0x04, (char)0x00, (char)0x1c,
+ (char)0x00, (char)0x04, (char)0x00, (char)0x10,
+ (char)0x80, (char)0x07, (char)0x00, (char)0x10,
+ (char)0x08, (char)0x07, (char)0x00, (char)0x10,
+ (char)0x0c, (char)0x07, (char)0x00, (char)0x10,
+ (char)0x1f, (char)0x06, (char)0x00, (char)0x10,
+ (char)0x1f, (char)0x06, (char)0x00, (char)0x1c,
+ (char)0x3f, (char)0x0f, (char)0x00, (char)0x1e,
+ (char)0xff, (char)0x1f, (char)0x00, (char)0x1f,
+ (char)0xff, (char)0x3f, (char)0x80, (char)0x1f,
+ (char)0xff, (char)0x3f, (char)0x80, (char)0x1f,
+ (char)0xff, (char)0x3f, (char)0x80, (char)0x1f
 };
 
 /* This is the function which creates cursors. On success it return