FMSLogo Code

Replace win32-specific clipboard code in the File API with platform-independent code.
This brings FMSLogo one step closer to running on GNU/Linux.
It also fixes a bug where a NUL character was written to the end of the clipboard file.

Fix a bug in the logic for 3-byte encodings of UTF-8.

Declare write_char_utf8 as "static", since it's not used outside this file.

Include debugheap.h to fix crashes when FMSLogo is built in debug mode without precompiled headers.

Extend DLLCALL to support passing PWSTR strings with 'U'
This enables Logo programs to call many more system functions.

Include debugheap.h, in case this file ever calls allocation routines

Refactoring: Combine boolean (is binary) with wxBOM (character encoding) into ENCODING.
This enables a clearer discription of a file stream's encoding requirements, as it
didn't make sense to use a BOM to describe a binary encoding.

Add infrastructure to keep character encoding with a FILE*.
This is an attempt to be able to read/write Unicode text while
maintaining a reasonable amount of backward-compatability.
A lot more work is needed to make the file API compatible with Unicode.

Merge in changes to print functions from trunk.

Refactoring: Rename new_line() to print_newline()
This more clearly explains what it does.