Fix merge for ACS's DropItem
Fix A_DropItem from merge
Add generic integer setters and getters for PInt and PFloat types
Minor PField changes.

- Rename FieldOffset and FieldType so they no longer have the "Field" prefix
- Add a Flags field.
Use PField and not PSymbolVariable for ACS's Get/SetUserVariable
Use PField instead of PSymbolVariable for SetMapThingUserData()
Use PField instead of PSymbolVariable for A_SetUserVar/Array
Remove FxGlobalVariable class
Remove unused GetVariableValue()
Change disassembly dumps to be controlled from one spot

- Instead of changing three places to turn disassembly dumps on and off,
  do it with just one place. As a side effect, this now handles the case
  where the dump file can't be opened.
Add VM opcodes NOP, LANG, and SANG

- To simplify code generation genericizing, add three new opcodes
  * NOP: No-Operation
  * LANG: Load Angle - load a BAM angle into a float reg as degrees
  * SANG: Save Angle - store a float reg into a BEM angle, converting from degrees
Mark PType's GetValueInt method as const
Add code generation simplification methods to PType

- To assist with using PType with DECORATE expression code generation,
  added GetStoreOp(), GetLoadOp(), and GetRegType() to PType.
Add PFixed and PArray types

- These are types that are stored as integers but otherwise handled as floating point values.
Set PStatePointer's TypeTableType in PType::StaticInit()

- It was forgotten about earlier.
Make PStruct::AddField() check for duplicates

- PStruct::AddField() now checks the symbol table for a symbol of the same
  name before adding a new field. If the name is in use, it returns NULL.
Use PField instead of PSymbolVariable for DECORATE expressions

- The type systems used by PField and FxExpression are completely
  incompatible, but I think I got the differences taken care of as far
  as ParseNativeVariable(), ParseUserVariable(), and FxClassMember are
  concerned.
- Support for declaring native bool variables has been removed for the time
  being. It wasn't used anyway.
- Removed PSymbolVariable.
DECORATE cleanup

- Remove some ExpVal stuff that wasn't used.