RFR(M) : 7104565 : trim jprt build targets

[David Chase]

webrev: http://cr.openjdk.java.net/~drchase/7104565/webrev.02/

Problem:
Debug builds are inconsistently named, and are not needed for usual JPRT testing, and consume lots of space and time.
#ifdef conventions are a little dubious (I'm just paraphrasing from the bug here).

Fix:
Pick up Tom Rodriguez's work towards a fix (95+% complete),
translate forward in time to current build, check for omissions and changes.

Fix includes:
replace #ifdef DEBUG and #ifdef FASTDEBUG with #ifdef ASSERT
consistently name the debug build "debug" instead of "jvmg"
remove "debug" targets from JPRT properties files.

Testing:
Jtreg locally
JPRT of usual compiler tests
Cross-checked old diffs with new diffs
JPRT of compiler regression tests
Manually check that appropriate -DASSERT flag is passed to compilations.

Noticeable changes:
"make debug", not "make jvmg"
JPRT of compiler regression tests is much faster and times out much less often.