RFR: 8183569: Remove duplicated flag limits in parse_xss and globals.hpp

[Ioi Lam]

We have the following in Arguments::parse_xss():

  const julong min_ThreadStackSize = 0;
  const julong max_ThreadStackSize = 1 * M;
  const julong min_size = min_ThreadStackSize * K;
  const julong max_size = max_ThreadStackSize * K;

which duplicates the min/max range specified in globals.hpp:

  product_pd(intx, ThreadStackSize, \
          "Thread Stack Size (in Kbytes)") \
          range(0, 1 * M) \

I added an API to query the min/max range of a flag, so parse_xss can be rewritten as

  const JVMTypedFlagLimit<intx>* limit = 
    JVMFlagLimit::get_range_at(FLAG_MEMBER_ENUM(ThreadStackSize))->cast<intx>();
  const julong min_size = limit->min() * K;
  const julong max_size = limit->max() * K;

-------------

Commit messages:
 - fixed typo
 - use type_traits to avoid lots of boiler-plate functions
 - step one

Changes: https://git.openjdk.java.net/jdk/pull/2688/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2688&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8183569
  Stats: 79 lines in 4 files changed: 59 ins; 2 del; 18 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2688.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2688/head:pull/2688

PR: https://git.openjdk.java.net/jdk/pull/2688