Fix the layout of the generator expression documentation.

Source/cmDocumentGeneratorExpressions.h

@@ -35,18 +35,20 @@
   "  $<TARGET_FILE_DIR:tgt>/$<TARGET_FILE_NAME:tgt>\n"                  \
   "  $<TARGET_LINKER_FILE_DIR:tgt>/$<TARGET_LINKER_FILE_NAME:tgt>\n"    \
   "  $<TARGET_SONAME_FILE_DIR:tgt>/$<TARGET_SONAME_FILE_NAME:tgt>\n"    \
+  "\n"                                                                  \
   "  $<TARGET_PROPERTY:tgt,prop>   = The value of the property prop\n"  \
-  "the target tgt. Note that tgt is not added as a dependency of the "  \
-  "target this expression is evaluated on.\n" \
+  "on the target tgt. Note that tgt is not added as a dependency of\n"  \
+  "the target this expression is evaluated on.\n"                       \
   "Boolean expressions:\n"                                              \
   "  $<AND:?[,?]...>           = '1' if all '?' are '1', else '0'\n"    \
   "  $<OR:?[,?]...>            = '0' if all '?' are '0', else '1'\n"    \
   "  $<NOT:?>                  = '0' if '?' is '1', else '1'\n"         \
   "where '?' is always either '0' or '1'.\n"                            \
+  ""
 
 #define CM_DOCUMENT_COMMAND_GENERATOR_EXPRESSIONS                       \
   CM_DOCUMENT_ADD_TEST_GENERATOR_EXPRESSIONS \
-  "Expressions with an implicit 'this' target:"                         \
+  "Expressions with an implicit 'this' target:\n"                       \
   "  $<TARGET_PROPERTY:prop>   = The value of the property prop on\n"   \
   "the target on which the generator expression is evaluated.\n"        \
   ""