Now using cmake as build system, creating libmfile.so, ready for 'make install'. All former tests passing.

	* do not write uninitialized memory to file
	* correct handling of double (float64) matrices

Changed 'load_spec' and 'save_spec' back to P_((const char *name, unsigned long *buf, int num)), because this is how it is expected by fera.

Change in minfo.c: MST_DIMSFIXED only says lines and columns are fixed, so why prohibit changing of filetype, etc? This caused e.g. matconv not to convert some spectra!

Changed the code so that it only checks for dimension conservation.

because this is used internally.