Some changes added to compile and run with Java 6 and Java 7.

- correction of errors with Javac 6:
    - target 1.5 and source empty.
  - correction of errors with Javadoc 7:
    - strange behavior when duplicate classes are given.

Change-Id: Ib814ede143f7799ef18e0fb1b733547519b8b0e5
Signed-off-by: Alvin Francis <nivlafx@gmail.com>

Conflicts:
	core/main.mk
Add experimental flag to support OpenJDK builds.

bug: 8992787

(cherry picked from commit d1dbe7f5a23bacdff086b4992e1d31a96da706c3)

Change-Id: Ie977d4f26ae8d3eee9d7b9cf2c0c270bee5b54b3
Signed-off-by: Alvin Francis <nivlafx@gmail.com>

Conflicts:
	core/combo/javac.mk
	core/main.mk
A few more Java7 related clean ups.

- Separate SDK checking from version checking and
  make messages clearer.
- Add explicit source & target versions for javac to
  make things clearer.
- Rename flag from EXPERIMENTAL_USE_JAVA7_OPENJDK to
  EXPERIMENTAL_USE_JAVA7.
- Allow Oracle JDK 1.7 to be used on Mac OS, since there's
  no official OpenJDK support for that platform.

Change-Id: I454d2c917ed78f03ec7559a99659fefe7e7d50f3
Add support for ALTERNATE_JAVAC

Bug: 12476356
Change-Id: Idd013031dc32a560bca76cca295bedcad55982b4
Increase the maximum javac heap size.

Java 7 needs more memory when you run some annotation tools.

Change-Id: Ia8b423244b9ce164500b24867fe2b3d10a5089ff
Build with java7 by default.

All introduce a flag LEGACY_USE_JAVA6 to force java6 builds.
This is an unsupported configuration, and provided temporarily
to iron out regressions and compare build output (if required.).

- Increment the version check sequence number.
- Move a more specific check (OpenJDK vs non OpenJDK) after
  the more general version check.
- Update the link in the version check error message to the
  "initializing" page instead of the "download" page. The latter
  talks about repo, mainly.

bug: 8992787

Change-Id: I313e17b1911768d4f3bc318c4162c53dec6eaf0d
Signed-off-by: Alvin Francis <nivlafx@gmail.com>

Conflicts:
	core/main.mk

Conflicts:
	core/config.mk
	core/main.mk
	envsetup.sh
Increase the maximum javac heap size again.

Change-Id: Ic3422650ea22977f3dcfd74505cb287ff6543c2d
javac: rename common_flags to avoid conflictions

 * Currently the flag conflicts with one seen in hardware/qcom
   rename to avoid issues.

Change-Id: I876fcd6a254f349dc5260509bcddb0367a7d49d8
Signed-off-by: Nick Reuter <nreuter85@gmail.com>