report MSVC target architecture

Report the MSVC target architecture during the build since Windows
users have to pick the correct one. The target architecture was already
being checked in order to set `g_msvs_variant`, so just move the logic
into a function, store it in a variable and use the result for both
actions. Helps with #165.
Merge pull request #166 from garfieldnate/feature-report-msvc-arch

report MSVC target architecture
Reversed last commit.
Added LICENSE.md which is the proper format for licenses on github.
Included links to nightlies and better formatting.
Updated README to include links to pages.
report MSVC target architecture

Report the MSVC target architecture during the build since Windows
users have to pick the correct one. The target architecture was already
being checked in order to set `g_msvs_variant`, so just move the logic
into a function, store it in a variable and use the result for both
actions. Helps with #165.
Merge pull request #168 from garfieldnate/feature-report-msvc-arch

report MSVC target architecture (redo)
nicer Tcl build printouts
remove dead lex_alias code

Remove the code related to the `lex_alias` variable in agent.h,
including the `expansion_node` and `alias_struct` structs. This code
is uncommented (except for a date and originating file), and the logic
in `get_lexeme` is unreachable because `lex_alias` is always NIL. The
original functionality seems to have been to skip actual string lexing
and instead programatically provide a list of tokens, perhaps for
testing the parser.
remove top_dir_stack

The `top_dir_stack` variable in agent.h is not used anywhere, so
remove it along with related code and the `dir_stack_struct` struct.

I believe that this was not meant to be accessed by client code because
it's usage involves manual memory allocation and deallocation.
remove commented extern C blocks
remove fake right paren logic

The functions to fake a right paren in the lexer were never used,
so removed all related code.
remove dollar-related lexing

The dollar (`$`) character is no longer used for any special lexemes,
so remove the special processing for it (originally added apparently in
1994).
factor out whitespace and comment skipping

Create a new function for skipping comments and whitespace in the
production lexer, and move the proper logic into it. Remove all of
the commented code that depends on `USE_TCL` not being defined,
as this is rather outdated and will not change in the future.
remove loading error code

Remove `load_errors_quit`, which was not used, and the possibly related
`respond_to_load_errors` calls, which were all commented out.
remove USE_TCL and USE_X_DISPLAY defines

Fixes #175. These defines are no longer used, so remove the related
sections (all commented code).
remove unused code related to lexer file stacks

`load_file` is the only function to call `stop_lex_from_file`, and it
does so right after the start function; `load_file` is never used, so
remove it and the stop function.

`start_lex_from_file`, then, is only called once, during lexer
initialization. `reading_from_top_level`, then, is always true, so
remove it and simplify all of the conditional blocks where it is used.
remove alternate_input_exit

`alternate_input_exit` was always true, so remove it and simplify
referring conditional blocks. This includes the code in `get_next_char`
for reading from a file.

Also comment/TODO the function that prints the lexer file location; this
has been useless ever since Soar stopped using file input here, but not
its uselessness is obvious.
rename alt vars to lex vars

Rename the `alternate_input_...` variables to reflect the fact that
they are the only input for the lexer. It seems that previously files
were the main input to the lexer, and that the `alternate` variables
were a way to put off lexing the file and instead lex an input string.