Change lib/gs/src/tool_utils.erl to select multiple browsers other than Netscape

[Kenji Rikitake]

git fetch git://github.com/jj1bdx/otp.git r13b03_gs_browser

Change lib/gs/src/tool_utils.erl to select multiple browsers other than
Netscape

This patch changes lib/gs/src/tools_utils.erl to choose multiple
browsers as in newly-added BROWSERS macro and internal functions
find_browser/1 and unix_url_command/1 so that the users can choose the
browsers other than currenly hard-coded "Netscape".

Originally from FreeBSD port patch files.

Regards,
Kenji Rikitake