Fix help and error messages.

tools/gn/functions_target.cc

Index: tools/gn/functions_target.cc
===================================================================
--- tools/gn/functions_target.cc	(revision 243014)
+++ tools/gn/functions_target.cc	(working copy)
@@ -60,11 +60,11 @@
     "\n"
     "  A component is a shared library, static library, or source set\n"
     "  depending on the component mode. This allows a project to separate\n"
-    "  out a build into shared libraries for faster devlopment (link time is\n"
+    "  out a build into shared libraries for faster development (link time is\n"
     "  reduced) but to switch to a static build for releases (for better\n"
     "  performance).\n"
     "\n"
-    "  To use this function you must set the value of the \"component_mode\n"
+    "  To use this function you must set the value of the \"component_mode\"\n"
     "  variable to one of the following strings:\n"
     "    - \"shared_library\"\n"
     "    - \"static_library\"\n"
@@ -285,8 +285,8 @@
     "  specify configs that apply to their dependents.\n"
     "\n"
     "  Depending on a group is exactly like depending directly on that\n"
-    "  group's deps. Direct dependent configs will get automatically fowarded\n"
-    "  through the group so you shouldn't need to use\n"
+    "  group's deps. Direct dependent configs will get automatically\n"
+    "  forwarded through the group so you shouldn't need to use\n"
     "  \"forward_dependent_configs_from.\n"
     "\n"
     "Variables\n"