[Merkaartor] Small compile fix

[Holger Schurig]

The same happens here:

$ make
g++ -c -pipe -g -Wall -W -D_REENTRANT -DVERSION="\"0.12\"" -DOSMARENDER -DLIBXML_STATIC -DLIBXSLT_STATIC -D_TTY_POSIX_ -DYAHOO -DQT_WEBKIT_LIB -DQT_SVG_LIB -DQT_XML_LIB -DQT_GUI_LIB -DQT_NETWORK_LIB -DQT_CORE_LIB -DQT_SHARED -I../../../share/qt4/mkspecs/linux-g++ -I. -I../../../include/qt4/QtCore -I../../../include/qt4/QtCore -I../../../include/qt4/QtNetwork -I../../../include/qt4/QtNetwork -I../../../include/qt4/QtGui -I../../../include/qt4/QtGui -I../../../include/qt4/QtXml -I../../../include/qt4/QtXml -I../../../include/qt4/QtSvg -I../../../include/qt4/QtSvg -I../../../include/qt4/QtWebKit -I../../../include/qt4/QtWebKit -I../../../include/qt4 -I. -IRender -Iqextserialport -IGPS -I../../../include/libxml2 -Itmp -Itmp -o tmp/obj_debug/qgpsdevice.o GPS/qgpsdevice.cpp
GPS/qgpsdevice.cpp: In member function 'int QGPSDevice::latDegrees()':
GPS/qgpsdevice.cpp:65: error: 'abs' was not declared in this scope
... plus a ton of of other warnings ...

"man abs" shows this:

NAME
       abs, labs, llabs, imaxabs - compute the absolute value of an integer

SYNOPSIS
       #include <stdlib.h>

       int abs(int j);


This happened on Debian SID, gcc 4.3.1.