Solaris awk lacks many POSIX features as listed below.  When any of
them is used, we use XPG4 awk at /usr/xpg4/bin/awk instead of Solaris
awk at /usr/bin/awk.

- Solaris awk does not support ENVIRON.
- Solaris awk does not support the function `tolower`.
- Solaris awk does not support user-defined functions.
- Solaris awk does not support `-F ERE' but only supports -F<char>.
- Solaris awk does not accept an option argument for `-F` in a
  separate word.  The option argument needs to be specified in the
  same command-line word as `-F<char>`.
- Solaris awk does not support the command-line option `-v var=value`

Co-authored-by: Ville Skyttä <ville.skytta@iki.fi>

The condition `$NF=2` in the awk script actually assigns a value `2`
to the last field instead of comparing it to `2` and always evaluates
to true.  I suspect it to be `NF >= 2`.

This could possibly be intended as `NF == 2` or `$NF == 2`, but
neither seems to work correctly.  The input contains the names of man
entries of the form ` perlxx <description>`, but the description is
usually given by more than one words, so restricting them by `NF == 2`
would be unreasonable.  On the other hand, there are no entries ending
with the word `2` so `$NF == 2` would produce no results.  This
condition was introduced from the beginning when the related code was
introduced in commit 4254f3a.  There does not seem to be any hints on
the background of `$NF=2`.