postmaster.opts in postgresql 9.3?
I have recently installed postgresql 9.4 from source

[pol@localhost inst]$ ./bin/psql --version
psql (PostgreSQL) 9.4.0
[pol@localhost inst]$ 


My install directory structure is as follows

/home/pol/Downloads/software/postgres/inst
[pol@localhost inst]$ ll
total 128
drwxrwxr-x.  2 pol pol  4096 Jan 29 05:42 bin
drwx------. 18 pol pol  4096 May  1 18:03 data
drwxrwxr-x.  6 pol pol  4096 Jan 29 05:42 include
-rw-r--r--.  1 pol pol 75392 Jan 29 05:44 INSTALL
-rw-rw-r--.  1 pol pol   158 Jan 29 05:45 install.txt
drwxrwxr-x.  4 pol pol  4096 Jan 29 05:42 lib
-rw-------.  1 pol pol 14718 May  2 17:47 logfile
-rw-rw-r--.  1 pol pol  2981 Jan 30 07:49 logfile.txt
-rw-rw-r--.  1 pol pol  5996 Apr  2 22:32 mytestdb.sql
drwxrwxr-x.  6 pol pol  4096 Jan 29 05:42 share


Then I searched for files name xxxx.opts

[pol@localhost inst]$ find . -name *.opts
./data/postmaster.opts


So, it exists in 9.4 - it appears from Googling that it generally lives in the data directory. I have never edited it manually.

[pol@localhost inst]$ more ./data/postmaster.opts 
/home/pol/Downloads/software/postgres/inst/bin/postgres "-D" "./data"
[pol@localhost inst]$


So, it appears that it still has a function in the system.