Need reviewer: Boot jdk needs to be 1.6, minor fixes to javadoc generation

[Kelly O'Hair]

Need reviewer: Boot jdk needs to be 1.6, minor fixes to javadoc  
generation

6973616: Update minimum boot jdk from 1.5 to 1.6
6971426: jdk/make/docs docs target does not work on windows

http://cr.openjdk.java.net/~ohair/openjdk7/jdk7-6971426%2b6973616/webrev/

The boot jdk really needs to be at least 1.6 for jdk7.

The jdk/make/docs/Makefile was recently re-worked but it wasn't very  
forgiving during partial
builds where some of the directories might not exist, or when  
unrelated platform specific directories
were purposely not included during the build.
Note that even though the javadocs can be built on windows machines  
now, developers might want
refrain from actually doing it on windows due to the build time hit  
and the fact that it is still not a
complete documentation set when generated on windows (jvmti.html is  
not generated on windows).

-kto