Current tip does not compile on windows

[tmodes]

Hg revision 0c73d8794377 does not compile on windows.

First: There appear several linker errors in the tools by the use of the not standard conform __progname variable:
error LNK2019: unresolved external symbol __progname referenced in function panoBasenameOfExecutable pano13.lib(sys_ansi.obj)

Second: CMake does call ctag-exuberant without to check for existence. Wrap it around a find_program

FIND_PROGRAM(_ctags ctags-exuberant)
IF(NOT ${_ctags} MATCHES "-NOTFOUND")
    ADD_CUSTOM_COMMAND( OUTPUT ctags POST_BUILD
                        COMMAND ${_ctags} -e *.c *.h tools/*.c
                        WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}/
                        COMMENT "Build TAGS file"
                      )
    ADD_CUSTOM_TARGET( TAGS DEPENDS ctags)
ENDIF()

[tmodes (tmodes)]

The attached patch fixes several issues with building libpano on Windows:
* It make the current tip to compile again.
* It add a workaround for an issue with CMake which did not correctly set some parameters for static 64-bit builds
* If fixes the mentioned ctags issue
* It adds option to build static or shared lib, with output of messages to commandline or gui (all Windows only)

The implementation adds 2 new files: sys_compat_unix.c and sys_compat_win.c. The CMake build system is already changed to use the correct one. This needs also be done for the configure/automake script.

[tmodes (tmodes)]

Fixed in changeset bb55bfdfa33e.
Needs testing if the change to build system work on all systems.