Error on Windows installing package to non-default library

Hi all,

I'm seeing an error on Windows when I try to install a package to a package 
library path that starts with a digit.  I can reproduce the error as follows 
using R-devel from Feb 24 on Windows advanced server:

badLib = "c:\\badExample\\2\\foo"
dir.create(badLib, recursive=TRUE)
z = .libPaths()
z = .libPaths(c(badLib, z))
z
[1] "c:\\badExample\\2\\foo"         "C:/falcon/sw/rw2010dev/library"

pkg = "c:\\falcon\\abind_1.1-0.zip"
install.packages(pkg, repos=NULL, lib=badLib)
package 'abind' successfully unpacked and MD5 sums checked
updating HTML package descriptions
Error in gsub("^URL: ../../../library", lib0, readLines(cfile)) :
       invalid backreference 2 in regular expression

After looking at src/library/utils/R/windows/linkhtml.R, it seems the error 
is that the "\\2" part of the path is interpreted by gsub as a back 
reference.

Changing "\\" to "/" in the library path fixes this issue:

okLib = chartr("\\", "/", badLib)
z = .libPaths(okLib)
z

[1] "c:/badExample/2/foo"            "C:/falcon/sw/rw2010dev/library"

install.packages(pkg, repos=NULL, lib=okLib)

package 'abind' successfully unpacked and MD5 sums checked
updating HTML package descriptions

So adding a call to chartr inside make.search.html would seem to be an
improvement (i.e, it looks good from here, but I haven't tested and
don't know if there are reasons why this would be a bad idea).  OTOH,
maybe this should have already happened in the call to .libPaths()?

This came up because on the Windows server I'm using, tempdir() contains a 
directory names "2" as part of the path --- and I want to be able to install 
package to temporary package libraries for testing purposes.

+ seth