[oe] empty strings

[Frans Meulenbroeks]

triggered by a remark on irc, I decided to do a grep on "" in all our recipes.
That gave some interesting observations. I've fixed a few things from
the type X += "" or X_append = ""
See the patch set I just send.

However there are also a few things that are not so obvious and for
which I want to ask your opinion, Some seem useless, others are
probably needed, but wanted to raise all issues that could be
unneeded.
Note that the recipes are just examples, ofthen there are more recipes
that have the same pattern.

libvorbis/libvorbis_1.2.3.bb:EXTRA_OECONF = ""
aircrack/aircrack_2.1.bb:DEPENDS = ""
apt/apt-native.inc:PACKAGES = ""  (this is a native recipe, isn't this
always the case for native recipes ? )
bind/bind_9.3.1.bb:RPEDENDS = "" (this one has a DEPENDS on openssl, I
would expect it also to rdepend on openssl in this case)
c3110x/cx3110x_1.1.bb:export LDFLAGS = ""
classpath/classpath.inc:RPROVIDES_${PN} = ""
fuse/fuse-module_2.7.4.bb:      LDFLAGS=""
glibc/glibc_2.10.1.bb:  CPPFLAGS="" oe_runconf (I was wondering of the
resetting CPPFLAGS is useful, didn't really dig into this one)
gs/gs-fonts-std_8.11.bb:HOMEPAGE = ""
gsoap/gsoap-native_2.7.13.bb:EXTRA_OEMAKE = ""
ipkg/ipkg-native.inc:PROVIDES = ""  (hm, no provides)
meta/staging-linkage_1.0.bb:SRC_URI = ""
psmisc/psmisc.inc:FILES_${PN} = "" (guess all files are added to other
packages, if that is so, should there be a line like this?)
tmake/tmake_1.11.bb:FILES = ""
ttf-fonts/ttf-hunkyfonts_0.3.0.bb:RRECOMMENDS_${PN}-dbg = "" (seems
somewhat strange to me)


this one also looked weird; guess it is ok but found it odd that these are reset
hplip/hplip_2.8.10.bb:EXTRA_OEMAKE = 'BUILD_SYS="" HOST_SYS=""'

I would like opinions on which of these constructs is useful and which
not. (and yes, I know an assingment may be used to nullify an earlier
assingment in an .inc file and I am also aware of cases where there is
something like X_virtclass_native = "" which is used to nullify
non-native assignments to X.

Enjoy, Frans