patch 8.0.1847: some build options don't have an example

Problem:    Some build options don't have an example.
Solution:   Add a couple more examples and compiler flags.
diff --git a/src/Makefile b/src/Makefile
index 5a6ad84..673875e 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -446,8 +446,10 @@
 # However, this may still cause problems, such as "import termios" failing.
 # Build two separate versions of Vim in that case.
 #CONF_OPT_PYTHON = --enable-pythoninterp
+#CONF_OPT_PYTHON = --enable-pythoninterp --with-python-command=python2.7
 #CONF_OPT_PYTHON = --enable-pythoninterp=dynamic
 #CONF_OPT_PYTHON3 = --enable-python3interp
+#CONF_OPT_PYTHON3 = --enable-python3interp --with-python3-command=python3.6
 #CONF_OPT_PYTHON3 = --enable-python3interp=dynamic
 
 # RUBY
@@ -611,8 +613,8 @@
 #CFLAGS = -g -Wall -Wextra -Wshadow -Wmissing-prototypes -Wunreachable-code -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1
 # Add -Wpedantic to find // comments and other C99 constructs.
 # Better disable Perl and Python to avoid a lot of warnings.
-#CFLAGS = -g -Wall -Wextra -Wshadow -Wmissing-prototypes -Wpedantic -Wunreachable-code -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1
-#CFLAGS = -g -O2 -Wall -Wextra -Wmissing-prototypes -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1 -DU_DEBUG
+#CFLAGS = -g -Wall -Wextra -Wshadow -Wmissing-prototypes -Wpedantic -Wunreachable-code -Wunused-result -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1
+#CFLAGS = -g -O2 -Wall -Wextra -Wshadow -Wmissing-prototypes -Wpedantic -Wunreachable-code -Wunused-result -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1
 #PYTHON_CFLAGS_EXTRA = -Wno-missing-field-initializers
 #MZSCHEME_CFLAGS_EXTRA = -Wno-unreachable-code -Wno-unused-parameter
 
diff --git a/src/version.c b/src/version.c
index 0b35c4f..fffdbf6 100644
--- a/src/version.c
+++ b/src/version.c
@@ -762,6 +762,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1847,
+/**/
     1846,
 /**/
     1845,