Fix included file path for modern perl

Contrary to the comment on 772d4b76, only paths starting with "./" or
"../" are considered relative to the current working directory by perl's
"do" function. So this patch converts all the relevant cases to use "./"
paths. This only affects MSVC.

Backpatch to all live branches.

src/tools/msvc/Install.pm

@@ -59,8 +59,8 @@ sub Install
 
 		# suppress warning about harmless redeclaration of $config
 		no warnings 'misc';
-		do "config_default.pl";
-		do "config.pl" if (-f "config.pl");
+		do "./config_default.pl";
+		do "./config.pl" if (-f "config.pl");
 	}
 
 	chdir("../../..")    if (-f "../../../configure");

src/tools/msvc/build.pl

@@ -23,7 +23,7 @@ use Mkvcbuild;
 
 if (-e "src/tools/msvc/buildenv.pl")
 {
-	do "src/tools/msvc/buildenv.pl";
+	do "./src/tools/msvc/buildenv.pl";
 }
 elsif (-e "./buildenv.pl")
 {
@@ -32,8 +32,8 @@ elsif (-e "./buildenv.pl")
 
 # set up the project
 our $config;
-do "config_default.pl";
-do "config.pl" if (-f "src/tools/msvc/config.pl");
+do "./config_default.pl";
+do "./config.pl" if (-f "src/tools/msvc/config.pl");
 
 my $vcver = Mkvcbuild::mkvcbuild($config);
 

src/tools/msvc/install.pl

@@ -18,7 +18,7 @@ use Install qw(Install);
 
 if (-e "src/tools/msvc/buildenv.pl")
 {
-	do "src/tools/msvc/buildenv.pl";
+	do "./src/tools/msvc/buildenv.pl";
 }
 elsif (-e "./buildenv.pl")
 {

src/tools/msvc/mkvcbuild.pl

@@ -23,7 +23,7 @@ print "Warning: no config.pl found, using default.\n"
   unless (-f 'src/tools/msvc/config.pl');
 
 our $config;
-do 'src/tools/msvc/config_default.pl';
-do 'src/tools/msvc/config.pl' if (-f 'src/tools/msvc/config.pl');
+do './src/tools/msvc/config_default.pl';
+do './src/tools/msvc/config.pl' if (-f 'src/tools/msvc/config.pl');
 
 Mkvcbuild::mkvcbuild($config);

src/tools/msvc/pgbison.pl

@@ -7,7 +7,7 @@ use File::Basename;
 
 # assume we are in the postgres source root
 
-do 'src/tools/msvc/buildenv.pl' if -e 'src/tools/msvc/buildenv.pl';
+do './src/tools/msvc/buildenv.pl' if -e 'src/tools/msvc/buildenv.pl';
 
 my ($bisonver) = `bison -V`;    # grab first line
 $bisonver = (split(/\s+/, $bisonver))[3];    # grab version number

src/tools/msvc/pgflex.pl

@@ -10,7 +10,7 @@ $ENV{CYGWIN} = 'nodosfilewarning';
 
 # assume we are in the postgres source root
 
-do 'src/tools/msvc/buildenv.pl' if -e 'src/tools/msvc/buildenv.pl';
+do './src/tools/msvc/buildenv.pl' if -e 'src/tools/msvc/buildenv.pl';
 
 my ($flexver) = `flex -V`;    # grab first line
 $flexver = (split(/\s+/, $flexver))[1];

src/tools/msvc/vcregress.pl

@@ -23,8 +23,8 @@ chdir "../../.." if (-d "../../../src/tools/msvc");
 my $topdir         = getcwd();
 my $tmp_installdir = "$topdir/tmp_install";
 
-do 'src/tools/msvc/config_default.pl';
-do 'src/tools/msvc/config.pl' if (-f 'src/tools/msvc/config.pl');
+do './src/tools/msvc/config_default.pl';
+do './src/tools/msvc/config.pl' if (-f 'src/tools/msvc/config.pl');
 
 # buildenv.pl is for specifying the build environment settings
 # it should contain lines like:
@@ -32,7 +32,7 @@ do 'src/tools/msvc/config.pl' if (-f 'src/tools/msvc/config.pl');
 
 if (-e "src/tools/msvc/buildenv.pl")
 {
-	do "src/tools/msvc/buildenv.pl";
+	do "./src/tools/msvc/buildenv.pl";
 }
 
 my $what = shift || "";