vl_phow.m: fix a bug in the 'color' option parsing

The colour specification should be case insensitive.

Resolves: #21
vl_phow.m: improve doc style
dist.mak: simplifies the post-doc target
about.html: fix links to personal pages
doc: apps.html, index.html: fix typos
vl_covdet.c: signal better the duplication of features when ambiguous orientations are detected

Resolves: #20
doc: compiling.html: change default Windows configuration to 64-bit

Fix the documentation so that the default Windows target is win64.
This is the case since at least vlfeat v0.9.14 in Makefile.mak
Makefile: clean up variables

This patch reorganizes the compilation and linker parameters by introducing two new variables, LINK_DLL_CLFAGS and LINK_DLL_LDFLAGS, containing the parameters needed to link the DLL.
It also removes redundant options when possible, and to clarify various special cases.
fix typos in vl_siftdescriptor.m documentation
Fix typo error
lbp.c: fix a bug requiring the output buffer to be cleared