add -ve numbers to Number parsing, and fixes constants generation. DOES NOT WORK, silently fails to emit code when using constants in a SET statement

Author: Dan Weatherill

wdl/Symbols.py

@@ -108,7 +108,7 @@
 IDENTIFIER_STARTCHARS = string.ascii_letters
 IDENTIFIER_CHARS = string.ascii_letters + string.digits + "_"
 
-NUMBER_STARTCHARS = string.digits
+NUMBER_STARTCHARS = string.digits + '-'
 NUMBER_CHARS = string.digits + "."
 
 STRING_STARTCHARS = "'" + '"'

wdl/wdlParser.py

@@ -1579,7 +1579,6 @@ def nbias(slot_number):
         consume(",")
 
         # must be a negative number...
-        consume("-")
         if found(NUMBER):
             cmd = token.cargo
         consume(NUMBER)