add req_source

[wielandp]

to enable debugging of "eval $string"

[wielandp]

An example of code, which can be debugged with this change:

use warnings;

my $code = '
print 1;
print 2;
print 3;
print 4;
print 5;
6;';

my @result = eval $code;

use Data::Dump qw{pp} ;
print STDERR "result = ". pp(@result)."\n" ;

[wielandp]

Thanks to @LanX for some hints :-)

[richterger]

In case it's a real file and not an eval, there the mapping via client2server needs to be applied. I will add it after the merge