(#14522) Don't read /proc/self/status on Solaris

/proc/self/status isn't a standard file on Solaris and can't be read as such.
Attempting to read it when using ruby 1.9.3 produces errors such as 'invalid
byte sequence in US-ASCII'. According to
http://www.ruby-forum.com/topic/163804, /proc/self/status is a sparse file with
a map at /proc/self/map to indicate which parts of the file to read. As a
stopgap measure, this commit simply returns false on Solaris, rather than
trying to read the file.