Cleaned up M4sh syntax for variable quoting, replaced shell 'if'
conditionals with M4sh AS_IF macro and shell 'case' with AS_CASE macro.
Properly quoted macro variables. Added comments to configure.ac
describing actions, commented out obsolete macros, commented obsolecent
macros, and added comments for major sections.
Corrected a Mingw linker error on the .EXE files adding
'--enable-auto-import' to their LD flags. Testing this commit on win32
shows that rigctld is now working properly. Will need to port this to
the Stable branch and test.
Replaced older local macros with newer replacements from GNU Autoconf
archive.
Nate Bargmann