emacs: add notmuch-logo.svg and use it in emacs mua on graphic displays

emacs/notmuch-logo.svg is handcrafted scalable vector graphics version
of the notmuch logo.

Emacs on graphic displays render this image four times in size compared
to the emacs/notmuch-logo.png, and the image is much sharper.

The rendered image size, 100x100 pixels, fits reasonably well with
text shown in various font sizes.

Scaling the image -- if desired -- may come in the future. For now
this is improvement on how the logo looked in notmuch-hello window.

debian/elpa-notmuch.elpa

@@ -1,3 +1,3 @@
 debian/tmp/usr/share/emacs/site-lisp/*.el
-debian/tmp/usr/share/emacs/site-lisp/notmuch-logo.png
+debian/tmp/usr/share/emacs/site-lisp/notmuch-logo.svg
 emacs/notmuch-pkg.el

emacs/Makefile.local

@@ -42,7 +42,7 @@ emacs_mua := $(dir)/notmuch-emacs-mua
 emacs_mua_desktop := $(dir)/notmuch-emacs-mua.desktop
 
 emacs_images := \
-	$(srcdir)/$(dir)/notmuch-logo.png
+	$(srcdir)/$(dir)/notmuch-logo.svg
 
 emacs_bytecode = $(emacs_sources:.el=.elc)
 emacs_docstrings = $(emacs_sources:.el=.rsti)

emacs/notmuch-hello.el

@@ -198,7 +198,7 @@ fields of the search."
 (defvar notmuch-hello-indent 4
   "How much to indent non-headers.")
 
-(defimage notmuch-hello-logo ((:type png :file "notmuch-logo.png")))
+(defimage notmuch-hello-logo ((:type svg :file "notmuch-logo.svg")))
 
 (defcustom notmuch-show-logo t
   "Should the notmuch logo be shown?"

emacs/notmuch-logo.svg

@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg xmlns="http://www.w3.org/2000/svg" width="100" height="100"
+     viewbox="0 0 100 100" fill="#000" stroke-width="2">
+  <circle cx="50" cy="5" r="5" />
+  <g transform="translate(50 20) rotate(20)">
+    <circle cx="-47" cy="0" r="3" />
+    <circle cx="47"  cy="0" r="3" />
+    <path d="M-47 -1  L0 -3  L47 -1 L47 1  L0 3  L-47 1 Z" />
+  </g>
+  <path d="M49 4  L45 88
+           A5 5  0  0 1  40 93  L20 93  A5 5  0  0 0  15 100
+           L85 100
+           A5 5  0  0 0  80 93  L60 93  A5 5  0  0 1  55 88
+           L55 90  L51 4 Z" />
+  <g fill="#fff" stroke="#000">
+    <rect x="7" y="33" width="30" height="18" />
+    <line x1="7"  y1="51" x2="18" y2="41" />
+    <line x1="37" y1="51" x2="26" y2="41" />
+    <polyline points="7 33  22 44  37 33" fill="none" />
+  </g>
+  <path d="M-18 0  A24 20  0  0 0  18 0" transform="translate(22 51.0)" />
+  <path d="M-18 0  A24 20  0  0 0  18 0" transform="translate(78 71.5)" />
+  <g fill="none" stroke="#000">
+    <path d="M9  53.0  l 12 -42  l 2 0  l 12 42" />
+    <path d="M91 73.5  l-12 -42  l-2 0  l-12 42" />
+  </g>
+</svg>