Reduce amount of empty space in which keypresses are detected

java/res/xml-sw600dp/row_symbols4.xml

java/res/xml-sw600dp/row_symbols_shift4.xml

java/res/xml-sw600dp/rows_number_normal.xml

java/res/xml-sw768dp/row_dvorak4.xml

java/res/xml-sw768dp/row_hebrew4.xml

java/res/xml-sw768dp/row_qwerty4.xml

java/res/xml-sw768dp/row_symbols4.xml

java/res/xml-sw768dp/row_symbols_shift4.xml

java/res/xml-sw768dp/rows_number_normal.xml

java/src/com/android/inputmethod/keyboard/KeyDetector.java