Support E notation for floating point numbers

patch by michalm; reviewed by slebresne for CASSANDRA-4927

CHANGES.txt

@@ -39,6 +39,7 @@
  * fix streaming progress report for compresed files (CASSANDRA-5130)
  * Coverage analysis for low-CL queries (CASSANDRA-4858)
  * Stop interpreting dates as valid timeUUID value (CASSANDRA-4936)
+ * Adds E notation for floating point numbers (CASSANDRA-4927)
 Merged from 1.1:
  * Simplify CompressedRandomAccessReader to work around JDK FD bug (CASSANDRA-5088)
  * Improve handling a changing target throttle rate mid-compaction (CASSANDRA-5087)

doc/cql3/CQL.textile

@@ -49,7 +49,7 @@ h3(#constants). Constants
 
 CQL defines 4 kinds of _implicitly-typed constants_: strings, numbers, uuids and booleans:
 * A string constant is an arbitrary sequence of characters characters enclosed by single-quote(@'@). One can include a single-quote in a string by repeating it, e.g. @'It''s raining today'@. Those are not to be confused with quoted identifiers that use double-quotes.
-* Numeric constants are either integer constant defined by @-?[0-9]+@ or a float constant defined by @-?[0-9]+.[0-9]*@.
+* Numeric constants are either integer constant defined by @'-'?[0-9]+@ or a float constant defined by @'-'?[0-9]+('.'[0-9]*)?([eE][+-]?[0-9+])?@.
 * A "UUID":http://en.wikipedia.org/wiki/Universally_unique_identifier constant is defined by @hex{8}-hex{4}-hex{4}-hex{4}-hex{12}@ where @hex@ is an hexadecimal character, e.g. @[0-9a-fA-F]@ and @{4}@ is the number of such characters.
 * A boolean constant is either @true@ or @false@ up to case-insensitivity (i.e. @True@ is a valid boolean constant).
 

src/java/org/apache/cassandra/cql3/Cql.g

@@ -1006,6 +1006,10 @@ fragment HEX
     : ('A'..'F' | 'a'..'f' | '0'..'9')
     ;
 
+fragment EXPONENT
+    : E ('+' | '-')? DIGIT+
+    ;
+
 INTEGER
     : '-'? DIGIT+
     ;
@@ -1019,7 +1023,8 @@ QMARK
  * to support multiple (see @lexer::members near the top of the grammar).
  */
 FLOAT
-    : INTEGER '.' DIGIT*
+    : INTEGER EXPONENT
+    | INTEGER '.' DIGIT* EXPONENT?
     ;
 
 IDENT