RFR: 8086005: Define __STDC_xxx_MACROS config macros globally via build system

[Kim Barrett]

Please review this change to the build of hotspot to globally define
the __STDC_xxx_MACROS macros via the command line, rather than
via #defines scattered through several header files.

CR:
https://bugs.openjdk.java.net/browse/JDK-8086005

Webrev:
http://cr.openjdk.java.net/~kbarrett/8086005/hs.00/
http://cr.openjdk.java.net/~kbarrett/8086005/hotspot.00/

Testing:
JPRT