minor cleanup in the core classes:

 * Documentation fixes (Class, Attributes)
 * Avoid creation of unnecessary temporary objects (AssertionError, Float, Double)

 hg status -m
M src/share/classes/java/io/Writer.java
M src/share/classes/java/lang/AssertionError.java
M src/share/classes/java/lang/Class.java
M src/share/classes/java/lang/Double.java
M src/share/classes/java/lang/Float.java
M src/share/classes/java/sql/PreparedStatement.java
M src/share/classes/java/sql/Statement.java
M src/share/classes/java/util/jar/Attributes.java