build: Rename last 'enable' options

Drop the 'enable-' prefix to conform to the best practices for naming
configuration options in Meson.

meson.build

@@ -507,7 +507,7 @@ if x11_enabled
     endif
   endif
 
-  enable_xinerama = get_option('enable-xinerama')
+  enable_xinerama = get_option('xinerama')
   if enable_xinerama != 'no'
     want_xinerama = enable_xinerama == 'yes'
     xinerama_dep = dependency('xinerama', required: want_xinerama)
@@ -560,7 +560,7 @@ have_vulkan = false
 vulkan_pkg_found = false
 vulkan_dep = []
 
-enable_vulkan = get_option('enable-vulkan')
+enable_vulkan = get_option('vulkan')
 if enable_vulkan == 'no'
   message('Vulkan support explicitly disabled')
 else
@@ -585,7 +585,7 @@ else
   endif
 endif
 
-cloudproviders_enabled = get_option('enable-cloudproviders')
+cloudproviders_enabled = get_option('cloudproviders')
 if cloudproviders_enabled
   cloudproviders_dep = dependency('cloudproviders', required: true)
   if cloudproviders_dep.found()

meson_options.txt

@@ -11,11 +11,11 @@ option('quartz-backend', type: 'boolean', value: true,
   description : 'Enable the macOS gdk backend (only when building on macOS)')
 
 # Optional dependencies
-option('enable-vulkan', type: 'combo', choices : ['yes', 'no', 'auto'], value : 'auto',
+option('vulkan', type: 'combo', choices : ['yes', 'no', 'auto'], value : 'auto',
   description : 'Enable support for the Vulkan graphics API')
-option('enable-xinerama', type: 'combo', choices : ['yes', 'no', 'auto'], value : 'auto',
+option('xinerama', type: 'combo', choices : ['yes', 'no', 'auto'], value : 'auto',
   description : 'Enable support for the Xinerama extension')
-option('enable-cloudproviders', type: 'boolean', value: false,
+option('cloudproviders', type: 'boolean', value: false,
   description : 'Enable the cloudproviders support')
 
 # Print backends