Switch to new 'libexec/git-core' directory layout

Git 1.6.0 will no longer place the dashed forms in 'bin' but
in 'libexec/git-core'.

This commit adjusts msysgit to support the new directory layout.
It also updates the git subproject to the first commit that
installs programs in the new location.  Note that this commit
only makes the basic adjustments.  A separate commit will modify
the installer.

Signed-off-by: Steffen Prohaska <prohaska@zib.de>

.gitignore

@@ -1,6 +1,7 @@
 /bin/git*
 /bin/cpio
 /home
+libexec/git-core
 /share/git-gui
 /share/gitk
 /share/git-core

git

@@ -1 +1 @@
-Subproject commit 76fbe95f5e2a38ce442fdde3db3f0cc0856d31c7
+Subproject commit 1ddfb58a5edcbdaf7371fe0036026c57aeed6a2c