Remove platform check for preventing use of yacc.

Replace with dev option "--grammar" which enables building of the grammar.
Some cleanup and generalization of searching for tools using ProgramFiles.


[SVN r19107]

tools/build

@@ -1 +1 @@
-Subproject commit 636e0d23790341857c24a5136f4f1d40d5780567
+Subproject commit 16cb4d5ef3fc5f21b7e75ee236b11d4f71aba4db