[Tilesathome] Minor optimizations to svg2png

[Moshe Sayag]

Hi everyone,

The subroutine svg2png (tilesGen.pl) is called many times during the
tiles creation, so every minor optimization can improve the overall
performance.

1. I've noticed that in every call to svg2png a new directory is
created ($TempDir), than a single file is created in it ($TempFile)
and at the end the directory is deleted.
Is this directory really necessary? Can't the file be created dircetly
under $Config{WorkingDirectory} ?

2. The line
my $Top = $ImageHeight - $Y1 - ($Y2 - $Y1);
can be replaced with
my $Top = $ImageHeight - $Y1 - $Height;
(after changing the lines order), or with
my $Top = $ImageHeight - $Y2;

Moshe