patch 9.0.0546: supporting Ruby 1.8 makes code complicated

Problem:    Supporting Ruby 1.8 makes code complicated.
Solution:   Drop Ruby 1.8 support, it is ancient. (Ken Takata, closes #11195)
diff --git a/src/Make_cyg_ming.mak b/src/Make_cyg_ming.mak
index 6c00bb2..55d13b1 100644
--- a/src/Make_cyg_ming.mak
+++ b/src/Make_cyg_ming.mak
@@ -441,7 +441,7 @@
 #	  RUBY=[Path to Ruby directory] (Set inside Make_cyg.mak or Make_ming.mak)
 #	  DYNAMIC_RUBY=yes (to load the Ruby DLL dynamically, "no" for static)
 #	  RUBY_VER=[Ruby version, eg 19, 22] (default is 22)
-#	  RUBY_API_VER_LONG=[Ruby API version, eg 1.8, 1.9.1, 2.2.0]
+#	  RUBY_API_VER_LONG=[Ruby API version, eg 1.9.1, 2.2.0]
 #			    (default is 2.2.0)
 #	    You must set RUBY_API_VER_LONG when changing RUBY_VER.
 #	    Note: If you use Ruby 1.9.3, set as follows:
@@ -466,9 +466,7 @@
  endif
 
  ifndef RUBY_PLATFORM
-  ifeq ($(RUBY_VER), 16)
-RUBY_PLATFORM = i586-mswin32
-  else ifneq ($(wildcard $(RUBY)/lib/ruby/$(RUBY_API_VER_LONG)/i386-mingw32),)
+  ifneq ($(wildcard $(RUBY)/lib/ruby/$(RUBY_API_VER_LONG)/i386-mingw32),)
 RUBY_PLATFORM = i386-mingw32
   else ifneq ($(wildcard $(RUBY)/lib/ruby/$(RUBY_API_VER_LONG)/x64-mingw32),)
 RUBY_PLATFORM = x64-mingw32
@@ -480,32 +478,20 @@
  endif
 
  ifndef RUBY_INSTALL_NAME
-  ifeq ($(RUBY_VER), 16)
-RUBY_INSTALL_NAME = mswin32-ruby$(RUBY_API_VER)
-  else
-   ifndef RUBY_MSVCRT_NAME
+  ifndef RUBY_MSVCRT_NAME
 # Base name of msvcrXX.dll which is used by ruby's dll.
 RUBY_MSVCRT_NAME = msvcrt
-   endif
-   ifeq ($(RUBY_PLATFORM),x64-mingw-ucrt)
+  endif
+  ifeq ($(RUBY_PLATFORM),x64-mingw-ucrt)
 RUBY_INSTALL_NAME = x64-ucrt-ruby$(RUBY_API_VER)
-   else ifeq ($(ARCH),x86-64)
+  else ifeq ($(ARCH),x86-64)
 RUBY_INSTALL_NAME = x64-$(RUBY_MSVCRT_NAME)-ruby$(RUBY_API_VER)
-   else
+  else
 RUBY_INSTALL_NAME = $(RUBY_MSVCRT_NAME)-ruby$(RUBY_API_VER)
-   endif
   endif
  endif
 
- ifeq (19, $(word 1,$(sort 19 $(RUBY_VER))))
-RUBY_19_OR_LATER = 1
- endif
-
- ifdef RUBY_19_OR_LATER
 RUBYINC = -I $(RUBY)/include/ruby-$(RUBY_API_VER_LONG) -I $(RUBY)/include/ruby-$(RUBY_API_VER_LONG)/$(RUBY_PLATFORM)
- else
-RUBYINC = -I $(RUBY)/lib/ruby/$(RUBY_API_VER_LONG)/$(RUBY_PLATFORM)
- endif
  ifeq (no, $(DYNAMIC_RUBY))
 RUBYLIB = -L$(RUBY)/lib -l$(RUBY_INSTALL_NAME)
  endif