meson.build: Bump libweston to 15

As we had changes like 9ae0a7ec and adeb634c which require a libweston major bump
uprev.

Signed-off-by: Marius Vlad <marius.vlad@collabora.com>

meson.build

@@ -10,7 +10,7 @@ project('weston',
 	license: 'MIT/Expat',
 )
 
-libweston_major = 14
+libweston_major = 15
 
 # libweston_revision is manufactured to follow the autotools build's
 # library file naming, thanks to libtool

westinyplus/meson.build

@@ -34,7 +34,7 @@ exe_westinyplus = executable(
     sources: [ 'src/main.cpp' ],
     dependencies: [ dependency('wayland-server'),
     dependency('weston'),
-    dependency('libweston-14') ],
+    dependency('libweston-15') ],
     include_directories : include_directories('.'),
     install: false
 )