RFR: 8033251: Use DWARF debug symbols for Linux 32-bit as default

[Erik Helin]

Hi all,

this patch changes the Linux Makefiles to use DWARF as the default debug 
symbol format for Linux 32-bit instead of STABS. The main arguments for 
using DWARF are:

   - DWARF provides a superior debugging experience compared to STABS.
   - STABS support in GCC/GDB is in maintenance mode [0].
   - External tools (e.g. perf on Linux) often understands DWARF but not
     STABS.
   - Compilation on 32-bit Linux can make use of precompiled headers.

Webrev:
http://cr.openjdk.java.net/~ehelin/8033251/webrev.00/

Testing:
- Compiling with GCC 4.3.4, GCC 4.7.3 and GCC 4.8.1
- JPRT

Thanks,
Erik

[0]: https://sourceware.org/ml/binutils/2013-01/msg00028.html