Conan: Updates to fix sudden linkage issues

We suddenly started to have some linking issues in the 0.27 branch after
the libcurl packages were updated in the conan-center repositories.
After some experimentation I took the following steps to fix up the
situation:

- Update conan to latest version
- Update of libcurl to the latest version available
- Use libcurl static libraries

Note that the change to use static libraries is just to make the
deployment step as easier as possible in the travis builds.

appveyor.yml

@@ -58,7 +58,7 @@ before_build:
     - cmd: cd envs
     - cmd: python -m virtualenv conan
     - cmd: conan/Scripts/activate
-    - cmd: python -m pip install conan==1.11.2
+    - cmd: python -m pip install conan==1.11.2 # TODO: Update to latest version (needs python 3)
     - cmd: cd ..
     - cmd: conan --version
     - cmd: conan remote add conan-bincrafters https://api.bintray.com/conan/bincrafters/public-conan

ci/install.sh

@@ -22,7 +22,7 @@ else
 fi
 
 python --version
-pip install conan==1.11.2
+pip install conan==1.17.0
 pip install codecov
 conan --version
 conan config set storage.path=~/conanData

conanfile.py

@@ -17,7 +17,7 @@ class Exiv2Conan(ConanFile):
                       )
 
     def configure(self):
-        self.options['libcurl'].shared = True
+        self.options['libcurl'].shared = False
         self.options['libcurl'].with_openssl = True
         self.options['gtest'].shared = True
 
@@ -34,7 +34,7 @@ class Exiv2Conan(ConanFile):
                 self.requires('gtest/1.8.1@bincrafters/stable')
 
         if self.options.webready and not os_info.is_macos:
-            self.requires('libcurl/7.61.1@bincrafters/stable')
+            self.requires('libcurl/7.64.1@bincrafters/stable')
 
         if self.options.xmp:
             self.requires('XmpSdk/2016.7@piponazo/stable') # from conan-piponazo