RFR (S): 8214816: os::read() should not transition to _thread_blocked with safepoint check on Solaris

[David Holmes]

Bug: https://bugs.openjdk.java.net/browse/JDK-8214816
webrev: http://cr.openjdk.java.net/~dholmes/8214816/webrev/

Please see the bug report for detailed background. In short summary all 
platforms now have the same os::read and os::read_at that doesn't do 
safepoint checks. Most of the changes are code deletions:

- removed unused os::restartable_read() method
- removed os::read from all os_*.cpp files and added shared inline 
definition in os.inline.hpp (checked all callsites already have 
os.inline.hpp included)
- removed os::read_at from all non-Windows os_*.cpp files and added 
shared definition in os_posix.cpp (simple wrapper to pread())
- fixed the return type of os::read and os::read_at to be ssize_t not 
size_t.

Also fixed os::read error handling in 
src/hotspot/share/compiler/directivesParser.cpp, and filed JDK-8216461 
to have a JFR usage of os::read_at fixed.

Also changed src/hotspot/share/runtime/arguments.cpp to use os::read as 
it no longer needs to avoid the thread-state-transition. Arguably we 
could go the other way here and remove os::read completely and use the 
native ::read on all platforms - there are already uses of ::read 
elsewhere in the code.

Testing: Mach5 tiers 1 - 3

Thanks,
David