Make:Allow for extension in tool names.

In some build environments executable programs have a specific file
extension.  The value of BIN_EXT is appended to the relevant tool file
names to allow for this.
The value of BIN_EXT is set, where appropriate, by the build environment
specific make helper (to .exe for Windows build environments).

.gitignore is updated to hide the new (.exe) files.

Change-Id: Icc32f64b750e425265075ad4e0dea18129640b86
diff --git a/.gitignore b/.gitignore
index a3b5e39..7447227 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,9 +11,11 @@
 # Ignore build products from tools
 tools/**/*.o
 tools/fip_create/fip_create
+tools/fip_create/fip_create.exe
 tools/cert_create/src/*.o
 tools/cert_create/src/**/*.o
 tools/cert_create/cert_create
+tools/cert_create/cert_create.exe
 
 # Ignore header files copied.
 tools/fip_create/firmware_image_package.h