6873059: Explicitly use -source 6 -target 6 when compiling with the boot jdk
Summary: The build fails if the bootstrap JDK defaults to <1.5
Reviewed-by: jcoomes
6879689: Fix warning about ignored return value when compiling with -O2
Summary: Store the return value of fwrite and check it matches the size of the array.
Reviewed-by: twisti, dholmes
6858208: jvm crash when specifying TypeProfileWidth=0 on jdk 6.0
Summary: Add an explicit check for TypeProfileWidth == 0 in record_klass_in_profile_helper() functions.
Reviewed-by: never, coleenp