Multiple improvements to build process

Restructure and document retroshare.pri variables and helper functions
Link sqlite statically like other libraries on Android
qmake has multiple win32-* specs match them correctly
Move a buch of generic thing to retroshare.pri instead of having them replocated
  accross project specific .pro
Fix retroshare-gui too many symbols exported on windows liking error by adding
  QMAKE_LFLAGS+=-Wl,--exclude-libs,ALL
Rename retroshare-gui/src/util/win32.h because the name is too prone to
  confusion and build conflicts
libreasapi avoid usage of cretar_prl link_prl that seems unreliable on some
  platforms
libreasapi rename LIBRESAPI_QT to more understendable LIBRESAPI_SETTINGS
Use use_*.pri instead of copy pasting error prone qmake snippets around
Expose bitdht option to retroshare.pri
Add RS_THREAD_LIB qmake variable for better crossplatform support
Move debug and profiling generic options to retroshare.pri (avoid copy/pasting)
Remove Qt script module in qmake as it is not available anymore

libbitdht/src/libbitdht.pro

@@ -6,23 +6,10 @@ CONFIG -= qt
 TARGET = bitdht
 DESTDIR = lib
 
+!include("use_libbitdht.pri"):error("Including")
+
 QMAKE_CXXFLAGS *= -Wall -DBE_DEBUG
 
-profiling {
-	QMAKE_CXXFLAGS -= -fomit-frame-pointer
-	QMAKE_CXXFLAGS *= -pg -g -fno-omit-frame-pointer
-}
-
-release {
-	# not much here yet.
-}
-
-#CONFIG += debug
-debug {
-        QMAKE_CXXFLAGS -= -O2 -fomit-frame-pointer
-        QMAKE_CXXFLAGS *= -g -fno-omit-frame-pointer
-}
-
 # treat warnings as error for better removing
 #QMAKE_CFLAGS += -Werror
 #QMAKE_CXXFLAGS += -Werror

libbitdht/src/use_libbitdht.pri

@@ -0,0 +1,5 @@
+DEPENDPATH *= $$system_path($$clean_path($${PWD}/../../libbitdht/src))
+INCLUDEPATH  *= $$system_path($$clean_path($${PWD}/../../libbitdht/src))
+LIBS *= -L$$system_path($$clean_path($${OUT_PWD}/../../libbitdht/src/lib/)) -lbitdht
+
+!equals(TARGET, bitdht):PRE_TARGETDEPS *= $$system_path($$clean_path($${OUT_PWD}/../../libbitdht/src/lib/libbitdht.a))