Fix hwdetect assembler clobbers

* src/hwfeatures.c (detect_x86_64_gnuc): Add missing %ebx assembler
clobbers.
(detect_x86_64_gnuc, detect_ia32_gnuc) [ENABLE_PADLOCK_SUPPORT]: Add
missing %ecx assembler clobbers.

detect_x86_64_gnuc() and detect_ia32_gnuc() have missing clobbers in
assembler statements. "%ebx" is missing in x86-64, probably because
copy-paste error (i386 code saves and restores %ebx to/from stack).
"%ecx" is missing from PadLock detection.

[v2]

• add GNU style changelog

• Signed-off-by: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>