Visual D 0.50.0-rc1

Changes from beta3:

• fix very terse update message when one newer product found
• vcxproj: fix D-Compiler option missing if no english VS language pack installed
• tweak colors for dark theme
• fix crash if document closed before semantic request callback completed (references or tooltip)
• fixed "go to definition" eventually not jumping to correct line after opening document
• mago: support multiple "live ranges" when LDC uses registers for locals
• mago: fix evaluating locals in registers
• updated full install to dmd 2.086.1 and ldc 1.16.0