Handling multi-line #ifs better

This is also a part of

 https://sourceforge.net/p/cscope/bugs/288/

Prior to this patch the code was checking to see if we were in an #if/#define by
looking at

 ppdefine == NO && my_yytext[0] != '#'

This worked fine for all #defines and single-line #ifs. This patch makes it work
for multi-line #ifs also
Fixed incorrectly-read filenames when re-building a database

Suppose you have a source file that contains just the line

#include <stdio.h>

If I build a database and then search for something (without disabling the
cross-reference update with -d) like this

cscope -c -b -i cscope.files -f cscope.out
cscope -c -L4 xxx

I get lots of bogus errors:

 Cannot open file

 Cannot open file /usr/include/stdio.h

 Cannot open file /usr/include/features.h

 Cannot open file /usr/include/getopt.h

 Cannot open file /usr/include/libio.h

 Cannot open file /usr/include/_G_config.h

 Cannot open file /usr/include/ctype.h

 Cannot open file /usr/include/stdc-predef.h

 Cannot open file /usr/include/endian.h

 Cannot open file /usr/include/gconv.h

 Cannot open file /usr/include/wchar.h

 Cannot open file /usr/include/xlocale.h

This happens because the code was reading these files with a trailing newline
and this newline was not being stripped. This patch strips the newline, and the
files can now be read properly