RFR: JDK-8145596 Enable debug symbols for all libraries

[Magnus Ihse Bursie]

For historical reasons, the FDS (Full Debug Symbols) project only 
enabled debug symbols for a few select libraries, since this was 
difficult to achieve in the old build. Also, the FDS project never 
enabled debug symbols for macosx on the JDK libraries.

With the new build system, debug symbols come for free for all 
libraries, and we actually have to do extra work to keep them out. :-&

We should just stop doing that. It hurts no-one to have proper debug 
information for all libraries, it might come in helpful, and just doing 
it everywhere would simplify build logic.

This is mainly a build change, but I'm cc:ing the component teams just 
in case.

This patch leverages JDK-8036003, but provides a cleaner implementation 
of this logic in the makefiles. Instead of the vague 
ENABLE_DEBUG_SYMBOLS, I have introduced three clearly defined variables:

COMPILE_WITH_DEBUG_SYMBOLS
COPY_DEBUG_SYMBOLS
ZIP_EXTERNAL_DEBUG_SYMBOLS

The various settings of --with-native-debug-symbols turns these 
variables on/off depending on what we want to achieve, and the makefiles 
check these variables to determine what compiler flags to use, whether 
to run objcopy (or similar) and whether to zip the extracted symbols, 
respectively.

A fourth variable (STRIP_DEBUG_SYMBOLS) is needed to fully complement 
this, but the way we handle stripping is complex in it's own right, and 
I've saved that for a separate patch.

Note that this patch intentionally does not affect the Hotspot build 
system. The variables for the hotspot build is kept unchanged. When the 
new build-infra based hotspot build system arrives, the functionality 
introduced in this patch will be automatically used. Until then, I 
prefer not to mess any more than necessary with the hotspot makefiles.

Bug: https://bugs.openjdk.java.net/browse/JDK-8145596
WebRev: 
http://cr.openjdk.java.net/~ihse/JDK-8145596-fix-native-debug-symbols-properly/webrev.01

/Magnus