How to enable long double precision for KCalc

If your machine supports the C data type long double and if you have a working libc you can enable long double precision for KCalc.

Here is what to do:

Check config-kcalc.h and see whether HAVE_LONG_DOUBLE is defined, i.e. you should be able to locate a line saying:
```
#define HAVE_LONG_DOUBLE 1
```
If you cannot find such a line your system doesn't support long double IEEE precision.
Edit the files kcalctype.h, configdlg.cpp, kcalc.cpp and kcalc_core.cpp and remove the lines:
```
#ifdef HAVE_LONG_DOUBLE
#undef HAVE_LONG_DOUBLE
#endif
```
Recompile KCalc.