[pca] make pca work easier on Linux

[Martin Paul]

Hi,

I know that some people use pca under non-Solaris systems like Linux, 
e.g. to read patch READMEs, download patches, etc. While this was 
already working fine when used in combination with the --fromfiles 
option, this was a little cumbersome. So I decided to make a few changes 
to allow pca to run without that option on foreign operating systems as 
well.

With the currently available development release (20100226-01), useful 
commands like these should work on Linux:

# Show all patches matching a pattern
   pca -p "Linux" -l total

# Download a patch
   pca -d 119254-72

# Look at a patch README
   pca -r 119254-72

Using pca to list missing or installed patches on a Linux system will 
always come up with empty patch lists. Do not expect pca to show correct 
installed/missing data for the ca. 100 Linux patches listed in the xref 
file. These are non-standard, "unbundled" patches.

Just in case somebody missed that: Using pca as a proxy server 
(pca-proxy.cgi) on Linux has worked before; some of you have been using 
that for quite some time now.

Martin.