RFR: JDK-8140661 Rename LDFLAGS_SUFFIX to LIBS

[Magnus Ihse Bursie]

The build system has not been good at separating LIBS from LDFLAGS. In 
fact, when we started doing this, the name "LDFLAGS_SUFFIX" was used for 
what is traditionally called LIBS. This unwieldy name has unfortunately 
been kept, and possibly as a cause of this, we have not been good at 
differing between flags to the linker and libraries needed to link with.

We should rename LDFLAGS_SUFFIX (and all of it's variants) to LIBS, and 
make sure we use LDFLAGS for flags and LIBS for libs.

I made this patch using sed to automatically replace LDFLAGS_SUFFIX with 
LIBS. I then manually checked all renamed instances, and verified that 
new names didn't clash with old names. I also used sed to rename 
LDFLAGS_JDKLIB_SUFFIX to JDKLIB_LIBS (and correspondingly for JDKEXE).

When I had verified that all replacements were sound, I also did some 
manual cleanup. It turned out that
a) we had not unified common libraries across platforms, e.g. repeating 
them for multiple individual platforms instead of using LIBS_unix. This 
was originally an explicit design goal to minimize spurious changes 
compared to the old build system, but that is not relevant any longer 
and needed to be fixed.
b) we had not properly separated LDFLAGS and LIBS, so in some cases we 
sent linker flags in LIBS (formerly LDFLAGS_SUFFIX, so it might be 
understandable) and library dependencies in LDFLAGS. (This is acceptable 
for some linkers, however, for good style, we should use LIBS for 
libraries consistently across platforms.)

I have fixed those issues, were I could find them.

Bug: https://bugs.openjdk.java.net/browse/JDK-8140661
WebRev: 
http://cr.openjdk.java.net/~ihse/JDK-8140661-rename-LDFLAGS_SUFFIX-to-LIBS/webrev.01

/Magnus