rules.mak: New logical functions for handling y/n values

Add new logical functions for handling y/n values like those we
use in CONFIG_FOO variables:
 lnot : logical NOT
 land : logical AND
 lor : logical OR
 lxor : logical XOR
 leqv : logical equality, inverse of lxor
 lif : like Make's $(if) but with an eq-like test

Based on an idea by Ákos Kovács <akoskovacs@gmx.com>.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
rules.mak: New string testing functions

Add new string testing functions which return a y/n result:
 eq : are two strings equal (ignoring leading/trailing space)?
 ne : are two strings unequal?
 isempty : is a string empty?
 notempty : is a string non-empty?

Based on an idea by Ákos Kovács <akoskovacs@gmx.com>.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Makefile.target: CONFIG_NO_* variables removed

CONFIG_NO_* variables replaced with the lnot logical function

Signed-off-by: Ákos Kovács <akoskovacs@gmx.com>
[PMM: fixed a few CONFIG_NO_* uses that were missed]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
default-configs/: CONFIG_GDBSTUB_XML removed

Makefile.target: Build gdbstub-xml.o only when
TARGET_XML_FILES is not empty.

Signed-off-by: Ákos Kovács <akoskovacs@gmx.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
ui/Makefile.objs: delete unnecessary cocoa.o dependency

Delete an unnecessary dependency for cocoa.o; we already have
a general rule that tells Make that we can build a .o file
from a .m source using an ObjC compiler, so this specific
rule is unnecessary. Further, it is using the dubious construct
"$(SRC_PATH)/$(obj)" to get at the source directory, which will
break when $(obj) is redefined as part of the preparation for
per-object library support.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>