infra: Add PRE_*_HOOKS for every step

Add PRE_*_HOOKS to all the different steps through which a package may go.

This will help avoid using POST_*_HOOKS to do tasks that should be done
in the PRE_*_HOOKS of the next step.
Otherwise, when the user would do a make foo-re<step>, this would not do
what was really intented, the POST_*_HOOK of the preceding step not
being executed.

Signed-off-by: Maxime Hadjinlian <maxime.hadjinlian@gmail.com>
[ThomasDS: rebase, add images hooks to manual]
Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

docs/manual/adding-packages-hooks.txt

@@ -13,17 +13,37 @@ of the package construction.
 
 The following hook points are available:
 
+* +LIBFOO_PRE_DOWNLOAD_HOOKS+
 * +LIBFOO_POST_DOWNLOAD_HOOKS+
+
+* +LIBFOO_PRE_EXTRACT_HOOKS+
 * +LIBFOO_POST_EXTRACT_HOOKS+
+
+* +LIBFOO_PRE_RSYNC_HOOKS+
 * +LIBFOO_POST_RSYNC_HOOKS+
+
 * +LIBFOO_PRE_PATCH_HOOKS+
 * +LIBFOO_POST_PATCH_HOOKS+
+
 * +LIBFOO_PRE_CONFIGURE_HOOKS+
 * +LIBFOO_POST_CONFIGURE_HOOKS+
+
+* +LIBFOO_PRE_BUILD_HOOKS+
 * +LIBFOO_POST_BUILD_HOOKS+
+
+* +LIBFOO_PRE_INSTALL_HOOKS+ (for host packages only)
 * +LIBFOO_POST_INSTALL_HOOKS+ (for host packages only)
+
+* +LIBFOO_PRE_INSTALL_STAGING_HOOKS+ (for target packages only)
 * +LIBFOO_POST_INSTALL_STAGING_HOOKS+ (for target packages only)
+
+* +LIBFOO_PRE_INSTALL_TARGET_HOOKS+ (for target packages only)
 * +LIBFOO_POST_INSTALL_TARGET_HOOKS+ (for target packages only)
+
+* +LIBFOO_PRE_INSTALL_IMAGES_HOOKS+
+* +LIBFOO_POST_INSTALL_IMAGES_HOOKS+
+
+* +LIBFOO_PRE_LEGAL_INFO_HOOKS+
 * +LIBFOO_POST_LEGAL_INFO_HOOKS+
 
 These variables are 'lists' of variable names containing actions to be